Port build-script from SDL3

[ci skip]

build-scripts/updaterev.sh

@@ -29,7 +29,7 @@ done
 rev=`sh showrev.sh 2>/dev/null`
 if [ "$rev" != "" ]; then
     if [ -n "$dist" ]; then
-        echo "$rev" > "$outdir/VERSION.txt"
+        echo "$rev" > "$outdir/REVISION.txt"
     fi
     echo "/* Generated by updaterev.sh, do not edit */" >"$header.new"
     if [ -n "$vendor" ]; then