Merge pull request git-for-windows#3466 from Berrysoft/main

Fix CMakeLists for MinGW.

Author: dscho

contrib/buildsystems/CMakeLists.txt

@@ -726,7 +726,13 @@ if(WIN32)
 	endif()
 
 	add_executable(headless-git ${CMAKE_SOURCE_DIR}/compat/win32/headless.c)
-	target_link_options(headless-git PUBLIC /NOLOGO /ENTRY:wWinMainCRTStartup /SUBSYSTEM:WINDOWS)
+	if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
+		target_link_options(headless-git PUBLIC -municode -Wl,-subsystem,windows)
+	elseif(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
+		target_link_options(headless-git PUBLIC /NOLOGO /ENTRY:wWinMainCRTStartup /SUBSYSTEM:WINDOWS)
+	else()
+		message(FATAL_ERROR "Unhandled compiler: ${CMAKE_C_COMPILER_ID}")
+	endif()
 elseif(UNIX)
 	target_link_libraries(common-main pthread rt)
 endif()