Disable util and libm-macros for optimized tests

These crates take time building in CI, especially with the release
profile having LTO enabled, but there isn't really any reason to test
them with different features or in release mode. Disable this to save
some CI runtime.

library/compiler-builtins/libm/ci/run.sh

@@ -77,8 +77,14 @@ if [ "${BUILD_ONLY:-}" = "1" ]; then
 else
     cmd="cargo test --all --target $target $extra_flags"
 
-    # Test once without intrinsics, once with intrinsics enabled
+    # Test once without intrinsics
     $cmd
+
+    # Exclude the macros and utile crates from the rest of the tests to save CI
+    # runtime, they shouldn't have anything feature- or opt-level-dependent.
+    cmd="$cmd --exclude util --exclude libm-macros"
+
+    # Test once with intrinsics enabled
     $cmd --features unstable-intrinsics
     $cmd --features unstable-intrinsics --benches