Add TODO checker to cg_gcc #2078

Job	Run time
build (--std-tests)	54s
build (--mini-tests)	51s
build (--test-libcore)	49s
build (--test-successful-rustc --nb-parts 2 --current-part 1)	53s
build (--test-successful-rustc --nb-parts 2 --current-part 0)	53s
success_gcc12	2s
	4m 22s

Provide feedback