[vcpkg] Clean up CMake build system (#10834)

There are quite a few changes to the CMake build system packaged up into
one set here:
* Added `toolsrc/cmake/utilities.cmake`, which contains the following:
  * `vcpkg_detect_compiler` -- get the name of the C++ compiler, as one
    of {gcc, clang, msvc}
  * `vcpkg_detect_standard_library` -- get the name of the standard
    library we're linking to, as one of {libstdc++, libc++, msvc-stl}
  * `vcpkg_detect_std_filesystem` -- figure out how to link and call
    into C++17's filesystem; whether one needs to link to `stdc++fs` or
    `c++fs`, and whether to use `<filesystem>` or
    `<experimental/filesystem>`.
* Added a `VCPKG_WARNINGS_AS_ERRORS`, split off from
  `VCPKG_DEVELOPMENT_WARNINGS`, which allows one to use the development
  warnings without passing -Werror
* Rename `DEFINE_DISABLE_METRICS` to `VCPKG_DISABLE_METRICS` -- the
  former will now print a deprecation message and set the latter.
* Now, print a deprecation message on `WERROR`; it doesn't do anything
  since the behavior it requested is now the default.
* Pass `-std=c++17` if the compiler allows it, instead of `-std=c++1z`
* Do some code movement
* Pass `USE_STD_FILESYSTEM` if possible, instead of only on minGW
  * Renamed to `VCPKG_USE_STD_FILESYSTEM`

Additionally, we now pass `/W4` in Debug mode on x86 in the Visual
Studio build system; this brings it in line with the CMake build system,
and the x64 Visual Studio build system.

And finally, we make some minor code changes to support compiling in
VCPKG_DEVELOPMENT_WARNINGS mode.

1 files changed, 14 insertions, 6 deletions

diff --git a/toolsrc/src/vcpkg-test/system.cpp b/toolsrc/src/vcpkg-test/system.cpp
index 41e27fe6d..70424f0b5 100644
--- a/toolsrc/src/vcpkg-test/system.cpp
+++ b/toolsrc/src/vcpkg-test/system.cpp
@@ -1,6 +1,5 @@
 #include <catch2/catch.hpp>
 
-#include <Windows.h>
 #include <string>
 #include <vcpkg/base/optional.h>
 #include <vcpkg/base/stringview.h>
@@ -8,6 +7,14 @@
 #include <vcpkg/base/strings.h>
 #include <vcpkg/base/system.h>
 
+#if defined(_WIN32)
+#define _NOMINMAX
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#else
+#include <stdlib.h>
+#endif
+
 using vcpkg::Optional;
 using vcpkg::StringView;
 using vcpkg::ZStringView;
@@ -39,16 +46,17 @@ namespace
         check_exit(VCPKG_LINE_INFO, exit_code != 0);
 #else  // ^^^ defined(_WIN32) / !defined(_WIN32) vvv
         std::string tmp;
-        tmp.reserve(varname.size() + value.size() + 1);
         tmp.append(varname.data(), varname.size());
         tmp.push_back('=');
-        if (value)
+        if (auto v = value.get())
         {
-            const auto& unpacked = value.value_or_exit(VCPKG_LINE_INFO);
-            tmp.append(unpacked);
+            tmp.append(*v);
         }
 
-        const int exit_code = putenv(tmp.c_str());
+        // putenv expects the string to never go out of scope
+        char* env_string = new char[tmp.size() + 1]; // overflow checked by tmp's null allocation
+        memcpy(env_string, tmp.data(), tmp.size());
+        const int exit_code = putenv(env_string);
         check_exit(VCPKG_LINE_INFO, exit_code == 0);
 #endif // defined(_WIN32)
     }