wscript: fix MSVC_TARGETS defined after XP compatibility check was made (thus fixing IndexOutOfRange error)

wscript

@@ -36,6 +36,7 @@ def options(opt):
 
 def configure(conf):
 	conf.load('fwgslib reconfigure compiler_optimizations')
+	conf.env.MSVC_TARGETS = ['x86' if not conf.options.ALLOW64 else 'x64']
 
 	# Force XP compatibility, all build targets should add subsystem=bld.env.MSVC_SUBSYSTEM
 	if conf.env.MSVC_TARGETS[0] == 'x86':
@@ -43,8 +44,6 @@ def configure(conf):
 	else:
 		conf.env.MSVC_SUBSYSTEM = 'WINDOWS'
 
-	conf.env.MSVC_TARGETS = ['x86' if not conf.options.ALLOW64 else 'x64']
-
 	# Load compilers early
 	conf.load('xcompile compiler_c compiler_cxx')