[Makefile]: add gcc-% and test-% targets

Makefile

@@ -58,6 +58,20 @@ clang-release:
 		BUILDTYPE=release \
 		BUILDDIR="build-$@"
 
+.PHONY: gcc-%
+gcc-%: GCC_VER=$(subst gcc-,,$@)
+gcc-%:
+	rm -f build
+	$(MAKE) build \
+		CC=gcc-$(GCC_VER) CXX=g++-$(GCC_VER) \
+		BUILDDIR="build-$@"
+
+.PHONY: test-%
+test-%: TEST_BUILD=$(subst test-,,$@)
+test-%:
+	$(MAKE) $(TEST_BUILD)
+	meson test -C build-$(TEST_BUILD)
+
 .PHONY: fibril-locked
 fibril-locked:
 	rm -f build