[profile] Build with -fms-extensions in MinGW mode

54902e0 added a use of
/alternatename via a #pragma comment(linker); in MinGW mode, this
requires building with -fms-extensions. (This flag is added to
SANITIZER_COMMON_CFLAGS in the toplevel CMakeLists.txt.)

This avoids a warning when building in MinGW mode (about an unknown
pragma being ignored), and presumably also makes the code work as
intended.

Differential Revision: https://reviews.llvm.org/D107620

(cherry picked from commit 94c001d)

Author: mstorsjo

compiler-rt/lib/profile/CMakeLists.txt

@@ -114,6 +114,9 @@ endif()
 append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ EXTRA_FLAGS)
 # XRay uses C++ standard library headers.
 string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+# The Windows specific code uses a #pragma comment(linker, ...) which requires
+# -fms-extensions on MinGW targets.
+append_list_if(MINGW -fms-extensions EXTRA_FLAGS)
 
 # This appears to be a C-only warning banning the use of locals in aggregate
 # initializers. All other compilers accept this, though.