Add support for building with MinGW (#9137)

* Add support for building with MinGW

Tested with MSYS2 MinGW 8.3.0, gcc-mcf.lhmouse MinGW 9.2.1,
and StephanTLavavej/mingw-distro!

* Add MinGW toolchain

From your MinGW configured shell you could just use vcpkg to
configure packages.

An x64-mingw triplet would look like:
```
set(VCPKG_TARGET_ARCHITECTURE x64)
set(VCPKG_CRT_LINKAGE dynamic)
set(VCPKG_LIBRARY_LINKAGE static)
set(VCPKG_ENV_PASSTHROUGH PATH)

set(VCPKG_CMAKE_SYSTEM_NAME MinGW)
```

* Add MinGW community tripplets

x64 tested with https://github.com/StephanTLavavej/mingw-distro
x86, arm64, arm tested with https://github.com/mstorsjo/llvm-mingw

4 files changed, 62 insertions, 12 deletions

diff --git a/scripts/cmake/vcpkg_common_definitions.cmake b/scripts/cmake/vcpkg_common_definitions.cmake
index 14cf460af..3a1818bf5 100644
--- a/scripts/cmake/vcpkg_common_definitions.cmake
+++ b/scripts/cmake/vcpkg_common_definitions.cmake
@@ -37,9 +37,12 @@ elseif(VCPKG_CMAKE_SYSTEM_NAME STREQUAL "Android")
     set(VCPKG_TARGET_IS_ANDROID 1)
 elseif(VCPKG_CMAKE_SYSTEM_NAME STREQUAL "FreeBSD")
     set(VCPKG_TARGET_IS_FREEBSD 1)
+elseif(VCPKG_CMAKE_SYSTEM_NAME STREQUAL "MinGW")
+    set(VCPKG_TARGET_IS_WINDOWS 1)
+    set(VCPKG_TARGET_IS_MINGW 1)
 endif()
 
-#Helper variable to identify the host path separator. 
+#Helper variable to identify the host path separator.
 if(CMAKE_HOST_WIN32)
     set(VCPKG_HOST_PATH_SEPARATOR ";")
 elseif(CMAKE_HOST_UNIX)
@@ -71,11 +74,15 @@ if(VCPKG_TARGET_IS_WINDOWS)
     set(VCPKG_TARGET_IMPORT_LIBRARY_PREFIX "")
     set(VCPKG_FIND_LIBRARY_SUFFIXES ".lib" ".dll") #This is a slight modification to CMakes value which does not include ".dll".
     set(VCPKG_FIND_LIBRARY_PREFIXES "" "lib") #This is a slight modification to CMakes value which does not include "lib".
-    ## For CYGWIN and Windows GNU, maybe VCPKG will support that in the future?
-    #set(VCPKG_TARGET_IMPORT_LIBRARY_SUFFIX ".dll.a")
-    #set(VCPKG_TARGET_IMPORT_LIBRARY_PREFIX "lib")
-    #set(VCPKG_FIND_LIBRARY_SUFFIXES ".dll" ".dll.a" ".a" ".lib")
-    #set(VCPKG_FIND_LIBRARY_PREFIXES "lib" "")
+elseif(VCPKG_TARGET_IS_MINGW)
+    set(VCPKG_TARGET_STATIC_LIBRARY_SUFFIX ".a")
+    set(VCPKG_TARGET_IMPORT_LIBRARY_SUFFIX ".dll.a")
+    set(VCPKG_TARGET_SHARED_LIBRARY_SUFFIX ".dll")
+    set(VCPKG_TARGET_STATIC_LIBRARY_PREFIX "lib")
+    set(VCPKG_TARGET_SHARED_LIBRARY_PREFIX "lib")
+    set(VCPKG_TARGET_IMPORT_LIBRARY_PREFIX "lib")
+    set(VCPKG_FIND_LIBRARY_SUFFIXES ".dll" ".dll.a" ".a" ".lib")
+    set(VCPKG_FIND_LIBRARY_PREFIXES "lib" "")
 elseif(VCPKG_TARGET_IS_OSX)
     set(VCPKG_TARGET_STATIC_LIBRARY_SUFFIX ".a")
     set(VCPKG_TARGET_IMPORT_LIBRARY_SUFFIX "")
diff --git a/scripts/cmake/vcpkg_configure_cmake.cmake b/scripts/cmake/vcpkg_configure_cmake.cmake
index c31955fb2..260f2471e 100644
--- a/scripts/cmake/vcpkg_configure_cmake.cmake
+++ b/scripts/cmake/vcpkg_configure_cmake.cmake
@@ -59,7 +59,7 @@
 ## * [poco](https://github.com/Microsoft/vcpkg/blob/master/ports/poco/portfile.cmake)
 ## * [opencv](https://github.com/Microsoft/vcpkg/blob/master/ports/opencv/portfile.cmake)
 function(vcpkg_configure_cmake)
-    cmake_parse_arguments(_csc 
+    cmake_parse_arguments(_csc
         "PREFER_NINJA;DISABLE_PARALLEL_CONFIGURE;NO_CHARSET_FLAG"
         "SOURCE_PATH;GENERATOR"
         "OPTIONS;OPTIONS_DEBUG;OPTIONS_RELEASE"
@@ -177,13 +177,13 @@ function(vcpkg_configure_cmake)
             "Invalid setting for VCPKG_LIBRARY_LINKAGE: \"${VCPKG_LIBRARY_LINKAGE}\". "
             "It must be \"static\" or \"dynamic\"")
     endif()
-    
+
     macro(check_both_vars_are_set var1 var2)
         if((NOT DEFINED ${var1} OR NOT DEFINED ${var2}) AND (DEFINED ${var1} OR DEFINED ${var2}))
             message(FATAL_ERROR "Both ${var1} and ${var2} must be set.")
         endif()
     endmacro()
-    
+
     check_both_vars_are_set(VCPKG_CXX_FLAGS_DEBUG VCPKG_C_FLAGS_DEBUG)
     check_both_vars_are_set(VCPKG_CXX_FLAGS_RELEASE VCPKG_C_FLAGS_RELEASE)
     check_both_vars_are_set(VCPKG_CXX_FLAGS VCPKG_C_FLAGS)
@@ -204,6 +204,8 @@ function(vcpkg_configure_cmake)
             set(VCPKG_CHAINLOAD_TOOLCHAIN_FILE "${SCRIPTS}/toolchains/osx.cmake")
         elseif(VCPKG_CMAKE_SYSTEM_NAME STREQUAL "FreeBSD")
             set(VCPKG_CHAINLOAD_TOOLCHAIN_FILE "${SCRIPTS}/toolchains/freebsd.cmake")
+        elseif(VCPKG_CMAKE_SYSTEM_NAME STREQUAL "MinGW")
+            set(VCPKG_CHAINLOAD_TOOLCHAIN_FILE "${SCRIPTS}/toolchains/mingw.cmake")
         endif()
     endif()
 
diff --git a/scripts/templates/portfile.in.cmake b/scripts/templates/portfile.in.cmake
index 62c53a6db..7ddf662e8 100644
--- a/scripts/templates/portfile.in.cmake
+++ b/scripts/templates/portfile.in.cmake
@@ -22,11 +22,12 @@
 #   VCPKG_TARGET_IS_OSX
 #   VCPKG_TARGET_IS_FREEBSD
 #   VCPKG_TARGET_IS_ANDROID
+#   VCPKG_TARGET_IS_MINGW
 #   VCPKG_TARGET_EXECUTABLE_SUFFIX
 #   VCPKG_TARGET_STATIC_LIBRARY_SUFFIX
 #   VCPKG_TARGET_SHARED_LIBRARY_SUFFIX
 #
-# 	See additional helpful variables in /docs/maintainers/vcpkg_common_definitions.md 
+# 	See additional helpful variables in /docs/maintainers/vcpkg_common_definitions.md
 
 # # Specifies if the port install should fail immediately given a condition
 # vcpkg_fail_port_install(MESSAGE "@PORT@ currently only supports Linux and Mac platforms" ON_TARGET "Windows")
@@ -39,10 +40,10 @@ vcpkg_download_distfile(ARCHIVE
 
 vcpkg_extract_source_archive_ex(
     OUT_SOURCE_PATH SOURCE_PATH
-    ARCHIVE ${ARCHIVE} 
+    ARCHIVE ${ARCHIVE}
     # (Optional) A friendly name to use instead of the filename of the archive (e.g.: a version number or tag).
     # REF 1.0.0
-    # (Optional) Read the docs for how to generate patches at: 
+    # (Optional) Read the docs for how to generate patches at:
     # https://github.com/Microsoft/vcpkg/blob/master/docs/examples/patching.md
     # PATCHES
     #   001_port_fixes.patch
diff --git a/scripts/toolchains/mingw.cmake b/scripts/toolchains/mingw.cmake
new file mode 100644
index 000000000..def98799f
--- /dev/null
+++ b/scripts/toolchains/mingw.cmake
@@ -0,0 +1,40 @@
+if(NOT _VCPKG_MINGW_TOOLCHAIN)

+set(_VCPKG_MINGW_TOOLCHAIN 1)

+if(CMAKE_HOST_SYSTEM_NAME STREQUAL "Windows")

+    set(CMAKE_CROSSCOMPILING OFF CACHE BOOL "")

+endif()

+

+# Need to override MinGW from VCPKG_CMAKE_SYSTEM_NAME

+set(CMAKE_SYSTEM_NAME Windows CACHE STRING "" FORCE)

+

+if(VCPKG_TARGET_ARCHITECTURE STREQUAL "x86")

+   set(CMAKE_SYSTEM_PROCESSOR i686 CACHE STRING "")

+elseif(VCPKG_TARGET_ARCHITECTURE STREQUAL "x64")

+   set(CMAKE_SYSTEM_PROCESSOR x86_64 CACHE STRING "")

+elseif(VCPKG_TARGET_ARCHITECTURE STREQUAL "arm")

+   set(CMAKE_SYSTEM_PROCESSOR armv7 CACHE STRING "")

+elseif(VCPKG_TARGET_ARCHITECTURE STREQUAL "arm64")

+   set(CMAKE_SYSTEM_PROCESSOR aarch64 CACHE STRING "")

+endif()

+

+foreach(lang C CXX)

+  set(CMAKE_${lang}_COMPILER_TARGET "${CMAKE_SYSTEM_PROCESSOR}-windows-gnu" CACHE STRING "")

+endforeach()

+

+get_property( _CMAKE_IN_TRY_COMPILE GLOBAL PROPERTY IN_TRY_COMPILE )

+if(NOT _CMAKE_IN_TRY_COMPILE)

+    string(APPEND CMAKE_C_FLAGS_INIT " ${VCPKG_C_FLAGS} ")

+    string(APPEND CMAKE_CXX_FLAGS_INIT " ${VCPKG_CXX_FLAGS} ")

+    string(APPEND CMAKE_C_FLAGS_DEBUG_INIT " ${VCPKG_C_FLAGS_DEBUG} ")

+    string(APPEND CMAKE_CXX_FLAGS_DEBUG_INIT " ${VCPKG_CXX_FLAGS_DEBUG} ")

+    string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " ${VCPKG_C_FLAGS_RELEASE} ")

+    string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " ${VCPKG_CXX_FLAGS_RELEASE} ")

+

+    string(APPEND CMAKE_SHARED_LINKER_FLAGS_INIT " ${VCPKG_LINKER_FLAGS} ")

+    string(APPEND CMAKE_EXE_LINKER_FLAGS_INIT " ${VCPKG_LINKER_FLAGS} ")

+    if(VCPKG_CRT_LINKAGE STREQUAL "static")

+        string(APPEND CMAKE_SHARED_LINKER_FLAGS_INIT "-static ")

+        string(APPEND CMAKE_EXE_LINKER_FLAGS_INIT "-static ")

+    endif()

+endif()

+endif()