[pve-devel] Relax gcc check in Makefile

[Dietmar Maurer]

> - Relax gcc check in Makefile so any gcc version 4.7 can be used.
>   Debian Sid has version 4.7.4

We encountered serious problems/crashes when using other versions, so I
hardcode that to make sure I always run the correct version.

> - Honor CC environment so compiling with non default gcc is
>   possible without changing symliks. Example:
>   make CC=gcc-4.7

AFAIK the kernel Makefile does not use CC environment.