Save the version in VERSION.txt instead of VERSION

Fixes https://github.com/libsdl-org/SDL/issues/6558

build-scripts/showrev.sh

@@ -5,8 +5,8 @@
 SDL_ROOT=$(dirname $0)/..
 cd $SDL_ROOT
 
-if [ -e ./VERSION ]; then
-    cat ./VERSION
+if [ -e ./VERSION.txt ]; then
+    cat ./VERSION.txt
     exit 0
 fi
 

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"
+        echo "$rev" > "$outdir/VERSION.txt"
     fi
     echo "/* Generated by updaterev.sh, do not edit */" >"$header.new"
     if [ -n "$vendor" ]; then