Fix libomp.a dune rule to handle missing paths gracefully

- Add &> /dev/null to the final fallback to suppress "No such file or directory" errors
- Add touch libomp.a to ensure the target is always created even if all copies fail

Author: taoeffect

src/quickjs/dune

@@ -56,7 +56,8 @@
     cp /usr/local/Cellar/libomp/17.0.6/lib/libomp.a . &> /dev/null \
     || cp /usr/lib/libgomp.a libomp.a &> /dev/null \
     || cp /usr/lib/gcc/x86_64-linux-gnu/*/libgomp.a libomp.a &> /dev/null \
-    || cp /usr/lib/gcc/aarch64-redhat-linux/15/libgomp.a libomp.a
+    || cp /usr/lib/gcc/aarch64-redhat-linux/15/libgomp.a libomp.a &> /dev/null \
+    || touch libomp.a
   "))
   (mode standard)
 )