Pass MAKECMDGOALS to unit test submake

Without this, `make build_tap_test_debug` calls `make` (default target)
in test/tap/tests/unit/ instead of `make debug`. The debug target adds
-DDEBUG which is needed to define __thread stubs like
mysql_thread___session_debug that are guarded by #ifdef DEBUG.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

test/tap/Makefile

@@ -31,7 +31,7 @@ tests_with_deps: tap test_deps
 
 .PHONY: unit_tests
 unit_tests:
-	cd tests/unit && CC=${CC} CXX=${CXX} ${MAKE}
+	cd tests/unit && CC=${CC} CXX=${CXX} ${MAKE} $(MAKECMDGOALS)
 
 
 .PHONY: clean_utils