Fix mac build, split PlistBuddy use to separate script, suppress errors

* There's no "add or replace" so we have to just delete and ignore if
  it fails, then add/set as normal.

scripts/set_plist_version.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+VERSION=$1
+PLIST=$2
+
+# Delete the key if it already exists
+/usr/libexec/PlistBuddy -c "Delete :CFBundleShortVersionString" "$PLIST" >/dev/null 2>&1
+
+# Now add with the right value
+/usr/libexec/PlistBuddy -c "Add :CFBundleShortVersionString string $VERSION" "$PLIST" || exit 1
+
+# Set identifier
+/usr/libexec/PlistBuddy -c "Set :CFBundleIdentifier org.renderdoc.qrenderdoc" "$PLIST" || exit 1