util/gitconfig: Make gitconfig a bash script

The gitconfig target has a few bashisms and would fail
silently on systems that use a POSIX standard sh (like Ubuntu dash).

Remove the code from the makefile and put it in a bash script that
is called by the gitconfig target.

Change-Id: I3bc8cf688a3ad211b57c8ca0e6b1e86c82dc6a37
Signed-off-by: Marc Jones <marcj303@gmail.com>
Reviewed-on: https://review.coreboot.org/22857
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
2 files changed