Fix make libs in CI

Hi, This is my first PR to RElibc, and hopefully not the last, In short I am exploring the project hoping that I might be able to make it mainstream target for gentoo. but I found that there is no make libc command in the CI so instead hopefully this should make things right

➜  relibc git:(master) make libc
make: *** No rule to make target 'libc'.  Stop.

Thanks