Prepare for the release of Xcode 4, which has working LTO

with static libraries.


git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@7280 8ced0084-cf51-0410-be5f-012b33b47a6e

Externals/libpng/SConscript

@@ -6,7 +6,7 @@ import sys
 if env.has_key('shared_png') and env['shared_png']:
 	Return()
 
-if env['HAVE_WX']:
+if env.has_key('HAVE_WX') and env['HAVE_WX']:
 	Return()	# Currently using libwxpng
 
 files = [
@@ -28,4 +28,4 @@ files = [
 	]
 
 env['CPPPATH'] += ['#Externals/libpng']
-env['LIBS'] += env.StaticObject(files)
+env['LIBS'] += env.StaticLibrary('png', files)