build-libvlc-for-mac.sh has wrong SDKROOT path for macOS 10.12

On 10.12 at least, this is the correct path:

@@ -8,10 +8,10 @@ info()
     echo "[${green}build${normal}] $1"
 }
 
-OSX_VERSION="10.11"
+OSX_VERSION="10.12"
 ARCH="x86_64"
 MINIMAL_OSX_VERSION="10.7"
-SDKROOT=`xcode-select -print-path`/Platforms/MacOSX.platform/Developer/SDKs/MacOSX$OSX_VERSION.sdk
+SDKROOT=`xcode-select -print-path`/SDKs/MacOSX.sdk
 UNSTABLE=yes
 
 usage()

Also, OSX_VERSION is not needed to be hardcoded, since MacOSX$OSX_VERSION.sdk is just a symlink to the former. Not sure if this is a recent change or not, sorry.