tools: rarezip: use system gzip on non-linux

tools/rarezip

@@ -6,4 +6,13 @@ test $size -gt 0 || exit 0
 
 printf "0: 1173 %.6x" $size | xxd -r -g0
 
-tools/gzip -c --no-name --best $1 | head --bytes=-8 | tail --bytes=+11
+if [[ "$OSTYPE" == "linux-gnu"* ]]; then
+  # use supplied gzip 1.2.4 for Linux
+  gzipbin="tools/gzip"
+else
+  # use system gzip on other systems
+  # NOTE: this might result in a non-matching file, but we don't really care
+  gzipbin="gzip -f"
+fi
+
+$gzipbin -c --no-name --best $1 | head --bytes=-8 | tail --bytes=+11