tools/build/make.py: drop workaround for cc --version not being parsed

Previously bsd.compiler.mk was not able to detect the compiler type for
Ubuntu's /usr/bin/cc unless we were invoking the /usr/bin/gcc symlink.
This problem has been fixed by 9c6954329a9285547881ddd60e393b7c55ed30c4
so we can drop the workaround from make.py.

Reviewed By: jrtc27
Differential Revision: https://reviews.freebsd.org/D28323

(cherry picked from commit 88db1cc9f197a376817ce27ba269348666bbd4b7)