contrib: don't use -arch flag of xcodebuild

It's only available since XCode4 on MacOSX 10.6

contrib/src/bghudappkit/rules.mak

@@ -20,7 +20,7 @@ bghudappkit: bghudappkit-git.tar.xz .sum-bghudappkit
 	$(MOVE)
 
 .bghudappkit: bghudappkit
-	cd $< && xcodebuild -arch $(ARCH) -sdk macosx$(OSX_VERSION)
+	cd $< && xcodebuild -sdk macosx$(OSX_VERSION)
 	install_name_tool -change @loader_path/../../../../../../../BGHUDAppKit.framework/Versions/A/BGHUDAppKit \
 								@loader_path/../../../../Versions/A/BGHUDAppKit \
 		$</build/Release/BGHUDAppKit.framework/Resources/BGHUDAppKitPlugin.ibplugin/Contents/MacOS/BGHUDAppKitPlugin

contrib/src/growl/rules.mak

@@ -23,6 +23,6 @@ growl: growl-$(GROWL_VERSION).tar.bz2 .sum-growl
 	touch $@
 
 .growl: growl
-	cd $< && xcodebuild -target Growl.framework -configuration Release -arch $(ARCH)
+	cd $< && xcodebuild -target Growl.framework -configuration Release
 	cd $< && cp -R -L build/Release/Growl.framework "$(PREFIX)"
 	touch $@

contrib/src/sparkle/rules.mak

@@ -21,6 +21,6 @@ sparkle: sparkle-$(SPARKLE_VERSION).zip .sum-sparkle
 	touch $@
 
 .sparkle: sparkle
-	cd $</Extras/Source\ Code && $(MAKE) && xcodebuild -arch $(ARCH)
+	cd $</Extras/Source\ Code && $(MAKE) && xcodebuild
 	cd $< && cp -R -L Extras/Source\ Code/build/release/Sparkle.framework "$(PREFIX)"
 	touch $@