intel/i915: warn the user about repeated execbuf ENOMEM after ~2s

By this point, the user may have noticed their game is not drawing any
new frames, so perhaps an error message might help.

This would also, of course, help identifying ENOMEM problems in our CI
runs.

Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37559>

src/intel/common/i915/intel_gem.h

@@ -160,6 +160,9 @@ i915_gem_execbuf_ioctl(int fd, const struct intel_device_info *info,
       if (likely(!(ret && errno == ENOMEM)))
          break;
 
+      if (unlikely(retries == 40))
+         fprintf(stderr, "intel: the execbuf ioctl keeps returning ENOMEM\n");
+
       os_time_sleep(100 * retries * retries);
    }