kbuild: scripts/ver_linux: don't set PATH

It would have saved both a bug submitter and me a few hours if
scripts/ver_linux had picked the same gcc as the build.

Since I can't see any reason why it fiddles with PATH at all this patch
therefore removes the PATH setting.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>