Use MinGW GCC with POSIX thread support when linking.

This changes from using WIN32 threads to POSIX threads when linking. MinGW (when using `libstdc++`) doesn't support C11 and C++11 threading support with WIN32 threads. This PR also makes WINE builds more resilient. Note that this will not affect any multi-threaded Rust code, which uses the Win32 API, calling `CreateThread` and `WaitForSingleObject` directly.

Author: Alexhuszagh

.changes/1123.json

@@ -0,0 +1,6 @@
+{
+    "description": "support external C/C++ dependencies using C11/C++11 threads for MinGW targets by switching linkers from `*-gcc` to `*gcc-posix`.",
+    "type": "added",
+    "issues": [1122],
+    "breaking": true
+}

.changes/591-1095.json

@@ -17,7 +17,7 @@
     },
     {
         "type": "changed",
-        "description": "updated powerpc64, riscv64, and sparc64 *-linux-gnu images to use a 6.x kernel instead of a 4.x kernel.",
+        "description": "updated powerpc64, riscv64, and sparc64 `*-linux-gnu` images to use a 6.x kernel instead of a 4.x kernel.",
         "breaking": true,
         "issues": [1094]
     }

docker/Dockerfile.i686-pc-windows-gnu

@@ -34,9 +34,11 @@ RUN mkdir -p /usr/lib/binfmt-support/ && \
 COPY windows-entry.sh /
 ENTRYPOINT ["/windows-entry.sh"]
 
+# for why we always link with pthread support, see:
+# https://github.com/cross-rs/cross/pull/1123#issuecomment-1312287148
 ENV CROSS_TOOLCHAIN_PREFIX=i686-w64-mingw32-
 ENV CROSS_SYSROOT=/usr/i686-w64-mingw32
-ENV CARGO_TARGET_I686_PC_WINDOWS_GNU_LINKER="$CROSS_TOOLCHAIN_PREFIX"gcc \
+ENV CARGO_TARGET_I686_PC_WINDOWS_GNU_LINKER="$CROSS_TOOLCHAIN_PREFIX"gcc-posix \
     CARGO_TARGET_I686_PC_WINDOWS_GNU_RUNNER=wine \
     CC_i686_pc_windows_gnu="$CROSS_TOOLCHAIN_PREFIX"gcc-posix \
     CXX_i686_pc_windows_gnu="$CROSS_TOOLCHAIN_PREFIX"g++-posix \

docker/Dockerfile.x86_64-pc-windows-gnu

@@ -32,9 +32,11 @@ RUN mkdir -p /usr/lib/binfmt-support/ && \
 COPY windows-entry.sh /
 ENTRYPOINT ["/windows-entry.sh"]
 
+# for why we always link with pthread support, see:
+# https://github.com/cross-rs/cross/pull/1123#issuecomment-1312287148
 ENV CROSS_TOOLCHAIN_PREFIX=x86_64-w64-mingw32-
 ENV CROSS_SYSROOT=/usr/x86_64-w64-mingw32
-ENV CARGO_TARGET_X86_64_PC_WINDOWS_GNU_LINKER="$CROSS_TOOLCHAIN_PREFIX"gcc \
+ENV CARGO_TARGET_X86_64_PC_WINDOWS_GNU_LINKER="$CROSS_TOOLCHAIN_PREFIX"gcc-posix \
     CARGO_TARGET_X86_64_PC_WINDOWS_GNU_RUNNER=wine \
     CC_x86_64_pc_windows_gnu="$CROSS_TOOLCHAIN_PREFIX"gcc-posix \
     CXX_x86_64_pc_windows_gnu="$CROSS_TOOLCHAIN_PREFIX"g++-posix \