Add CI compiling rustc #1859

Job	Run time
build (--test-successful-rustc --nb-parts 2 --current-part 1)	46s
build (--test-successful-rustc --nb-parts 2 --current-part 0)	42s
build (--mini-tests)	52s
build (--std-tests)	52s
build (--test-libcore)	49s
success_gcc12	2s
	4m 3s

Provide feedback