gpu_renderer: sys_util::debug is only used on x86_64.
gpu_renderer: sys_util::debug is only used on x86_64.

Including it on other architectures causes an unused symbol error.

BUG=b:158290206
TEST=cargo test

Change-Id: If47cc3618c2aaa789fc0c7c7c26ed0e3e0bda621
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2283336
Reviewed-by: Zach Reizner <3374927928a53d04457674c546bd4de57c2044ec@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Andrew Walbran <91a7c1b7f9f624e0ed1b099dc85ecb6025941ee9@google.com>

google/crosvm,google/crosvm,google/crosvm,google/crosvm