Compile c/objective-c code max compatiblity when RELEASE

bitcoin-qt.pro

@@ -24,6 +24,8 @@ UI_DIR = build
 contains(RELEASE, 1) {
     # Mac: compile for maximum compatibility (10.5, 32-bit)
     macx:QMAKE_CXXFLAGS += -mmacosx-version-min=10.5 -arch i386 -isysroot /Developer/SDKs/MacOSX10.5.sdk
+    macx:QMAKE_CFLAGS += -mmacosx-version-min=10.5 -arch i386 -isysroot /Developer/SDKs/MacOSX10.5.sdk
+    macx:QMAKE_OBJECTIVE_CFLAGS += -mmacosx-version-min=10.5 -arch i386 -isysroot /Developer/SDKs/MacOSX10.5.sdk
 
     !windows:!macx {
         # Linux: static link