Set macos-min-version for C files too

Should fix another 10.7 issues (Nasal code is .c)

CMakeLists.txt

@@ -178,6 +178,7 @@ if(APPLE)
 # this should be handled by setting CMAKE_OSX_DEPLOYMENT_TARGET
 # but it's not working reliably, so forcing it for now
   SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mmacosx-version-min=10.7")
+  SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mmacosx-version-min=10.7")
 endif()
 
 if(${CMAKE_SYSTEM_NAME} MATCHES "Linux" OR