Forward CARGO_BUILD_FLAGS to ui_test test suite

Author: oli-obk

miri

@@ -135,7 +135,7 @@ test|test-debug|bless|bless-debug)
     # Then test, and let caller control flags.
     # Only in root project and ui_test as `cargo-miri` has no tests.
     cargo test $CARGO_BUILD_FLAGS "$@"
-    cargo test --manifest-path ui_test/Cargo.toml "$@"
+    cargo test $CARGO_BUILD_FLAGS --manifest-path ui_test/Cargo.toml "$@"
     ;;
 run|run-debug)
     # Scan for "--target" to set the "MIRI_TEST_TARGET" env var so