Fix #570: Honor #![no_builtins] attribute by passing -fno-builtin to … #2067

Job	Run time
build (--test-successful-rustc --nb-parts 2 --current-part 0)	50s
build (--test-successful-rustc --nb-parts 2 --current-part 1)	52s
build (--test-libcore)	49s
build (--std-tests)	51s
build (--mini-tests)	53s
success_gcc12	3s
	4m 18s

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