[PATCH] Make mkcompile_h use LANG=C and LC_ALL=C for $CC -v

Fix a minor bug in mkcompile_h.  As one can see, the current locale is used
while getting the version of gcc.  This produces problems when a locale
other than C or en_US is used.  As an example, my /proc/version contains
Turkish characters in iso-8859-9 encoding.

This patch fixes this issue by making sure that the C locale is used to get
gcc's version.

Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>