Fix libcds on MinGW

plugins/CMakeLists.txt

@@ -9,6 +9,13 @@ IF(LMMS_BUILD_APPLE)
 	SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
 ENDIF()
 
+IF(MINGW_PREFIX)
+	# There's a bug in some CMake or MinGW versions that passes -std=c++11 when
+	# compiling C files (e.g. fmopl.c). Remove -Werror for plugins to work
+	# around this.
+	STRING(REPLACE "-Werror " "" CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
+ENDIF()
+
 INCLUDE_DIRECTORIES(
 	${SAMPLERATE_INCLUDE_DIRS}
 	"${CMAKE_BINARY_DIR}/src"