Add runtime option to build script

I'm having a serious case of the Mondays...

Author: buchwasa

src/osx/Installer.Mac/build.sh

@@ -22,6 +22,10 @@ case "$i" in
     CONFIGURATION="${i#*=}"
     shift # past argument=value
     ;;
+    --runtime=*)
+    RUNTIME="${i#*=}"
+    shift
+    ;;
     --version=*)
     VERSION="${i#*=}"
     shift # past argument=value
@@ -45,7 +49,7 @@ COMPONENTOUT="$COMPONENTDIR/com.microsoft.gitcredentialmanager.component.pkg"
 DISTOUT="$OUTDIR/gcm-osx-x64-$VERSION.pkg"
 
 # Layout and pack
-"$INSTALLER_SRC/layout.sh" --configuration="$CONFIGURATION" --output="$PAYLOAD" || exit 1
+"$INSTALLER_SRC/layout.sh" --configuration="$CONFIGURATION" --output="$PAYLOAD" --runtime="$RUNTIME" || exit 1
 "$INSTALLER_SRC/pack.sh" --payload="$PAYLOAD" --version="$VERSION" --output="$COMPONENTOUT" || exit 1
 "$INSTALLER_SRC/dist.sh" --package-path="$COMPONENTDIR" --version="$VERSION" --output="$DISTOUT" || exit 1