build: Robust version checking helpers with `printf`

build: Robust version checking helpers with `printf`

This commit updates the compiler version checking helpers so that they also
work under environments like Darwin. It turns out that the behavior of
`echo` can be different in different environments, while `printf` seems to
be well defined.

Signed-off-by: Simon Kuenzer <simon@unikraft.io>
Reviewed-by: Alexander Jung <alex@unikraft.io>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Closes: #1034