metal: Update shader compilation script with fixes for newer xcode versions and for running on older platforms

src/render/metal/build-metal-shaders.sh

@@ -6,13 +6,17 @@ cd `dirname "$0"`
 
 generate_shaders()
 {
-    platform=$1
-    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/usr/bin/metal -std=$platform-metal1.1 -Wall -O3 -o ./sdl.air ./SDL_shaders_metal.metal || exit $?
-    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/usr/bin/metal-ar rc sdl.metalar sdl.air || exit $?
-    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/usr/bin/metallib -o sdl.metallib sdl.metalar || exit $?
-    xxd -i sdl.metallib | perl -w -p -e 's/\Aunsigned /const unsigned /;' >./SDL_shaders_metal_$platform.h
+	fileplatform=$1
+    compileplatform=$2
+    sdkplatform=$3
+    minversion=$4
+    xcrun -sdk $sdkplatform metal -c -std=$compileplatform-metal1.1 -m$sdkplatform-version-min=$minversion -Wall -O3 -o ./sdl.air ./SDL_shaders_metal.metal || exit $?
+    xcrun -sdk $sdkplatform metal-ar rc sdl.metalar sdl.air || exit $?
+    xcrun -sdk $sdkplatform metallib -o sdl.metallib sdl.metalar || exit $?
+    xxd -i sdl.metallib | perl -w -p -e 's/\Aunsigned /const unsigned /;' >./SDL_shaders_metal_$fileplatform.h
     rm -f sdl.air sdl.metalar sdl.metallib
 }
 
-generate_shaders osx
-generate_shaders ios
+generate_shaders osx osx macosx 10.11
+generate_shaders ios ios iphoneos 8.0
+generate_shaders tvos ios appletvos 9.0