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

3 files changed, 18 insertions, 7 deletions

diff --git a/toolsrc/src/vcpkg.cpp b/toolsrc/src/vcpkg.cpp
index 2dd13f43d..1f212dd94 100644
--- a/toolsrc/src/vcpkg.cpp
+++ b/toolsrc/src/vcpkg.cpp
@@ -263,7 +263,18 @@ static void load_config()
 
 #if defined(_WIN32)
 // note: this prevents a false positive for -Wmissing-prototypes on clang-cl
-int wmain(int, const wchar_t* const*);
+int wmain(int, const wchar_t* const* const);
+
+#if !defined(_MSC_VER)
+#include <shellapi.h>
+int main(int argc, const char* const* const /*argv*/)
+{
+    wchar_t **wargv;
+    wargv = CommandLineToArgvW(GetCommandLineW(), &argc);
+    return wmain(argc, wargv);
+}
+#endif
+
 int wmain(const int argc, const wchar_t* const* const argv)
 #else
 int main(const int argc, const char* const* const argv)
diff --git a/toolsrc/src/vcpkg/base/hash.cpp b/toolsrc/src/vcpkg/base/hash.cpp
index 11df3e329..81635b875 100644
--- a/toolsrc/src/vcpkg/base/hash.cpp
+++ b/toolsrc/src/vcpkg/base/hash.cpp
@@ -123,9 +123,9 @@ namespace vcpkg::Hash
     void top_bits(T) = delete;
 
     static constexpr uchar top_bits(uchar x) noexcept { return x; }
-    static constexpr uchar top_bits(std::uint32_t x) noexcept { return (x >> 24) & 0xFF; }
-    static constexpr uchar top_bits(std::uint64_t x) noexcept { return (x >> 56) & 0xFF; }
-    static constexpr uchar top_bits(UInt128 x) noexcept { return top_bits(x.top); }
+    [[maybe_unused]] static constexpr uchar top_bits(std::uint32_t x) noexcept { return (x >> 24) & 0xFF; }
+    [[maybe_unused]] static constexpr uchar top_bits(std::uint64_t x) noexcept { return (x >> 56) & 0xFF; }
+    [[maybe_unused]] static constexpr uchar top_bits(UInt128 x) noexcept { return top_bits(x.top); }
 
     // treats UIntTy as big endian for the purpose of this mapping
     template<class UIntTy>
@@ -145,7 +145,7 @@ namespace vcpkg::Hash
             for (uchar& ch : buff)
             {
                 ch = top_bits(tmp);
-                tmp <<= 8;
+                tmp = UIntTy(tmp << 8);
             }
 
             for (const auto byte : buff)
diff --git a/toolsrc/src/vcpkg/base/system.cpp b/toolsrc/src/vcpkg/base/system.cpp
index c84b7f8be..5a446a330 100644
--- a/toolsrc/src/vcpkg/base/system.cpp
+++ b/toolsrc/src/vcpkg/base/system.cpp
@@ -378,7 +378,7 @@ namespace vcpkg
 
         g_ctrl_c_state.transition_to_spawn_process();
         auto clean_env = compute_clean_environment(extra_env, prepend_to_path);
-        windows_create_process(cmd_line, clean_env.data(), process_info, NULL);
+        windows_create_process(cmd_line, clean_env.data(), process_info, 0);
 
         CloseHandle(process_info.hThread);
 
@@ -542,7 +542,7 @@ namespace vcpkg
     {
         HKEY k = nullptr;
         const LSTATUS ec =
-            RegOpenKeyExW(reinterpret_cast<HKEY>(base_hkey), Strings::to_utf16(sub_key).c_str(), NULL, KEY_READ, &k);
+            RegOpenKeyExW(reinterpret_cast<HKEY>(base_hkey), Strings::to_utf16(sub_key).c_str(), 0, KEY_READ, &k);
         if (ec != ERROR_SUCCESS) return nullopt;
 
         auto w_valuename = Strings::to_utf16(valuename);