kbuild: fix a compile warning

gcc-4.4.1:

 HOSTCC  scripts/basic/fixdep
scripts/basic/fixdep.c: In function 'traps':
scripts/basic/fixdep.c:377: warning: dereferencing type-punned pointer will break strict-aliasing rules
scripts/basic/fixdep.c:379: warning: dereferencing type-punned pointer will break strict-aliasing rules

(Apparently -fno-strict-aliasing will fix this too)

Signed-off-by: WANG Cong <amwang@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>