scons: Remove redundant code.

-fvisibility=hidden is already elsewhere for the whole tree.

src/gallium/drivers/svga/SConscript

@@ -6,9 +6,6 @@ if env['suncc']:
 	print 'warning: not building svga'
 	Return()
 
-if env['platform'] in ['linux']:
-	env.Append(CCFLAGS = ['-fvisibility=hidden'])
-
 if env['gcc']:
 	env.Append(CPPDEFINES = [
 		'HAVE_STDINT_H',