osx: Specify minimum version for C files too

CMakeLists.txt

@@ -187,6 +187,7 @@ if(NOT MSVC)
 	if(IOS)
 	elseif(APPLE AND NOT CMAKE_CROSSCOMPILING)
         # We want C++11, so target 10.7+
+        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mmacosx-version-min=10.7")
 		set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mmacosx-version-min=10.7 -stdlib=libc++ -U__STRICT_ANSI__")
 		set(CMAKE_XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++")
 	else()