vim: _FORTIFY_SOURCE=2 be gone

vim will abort in many places with this setting.  Replace
it with the benign _FORTIFY_SOURCE=1.

Signed-off-by: Joe Slater <joe.slater@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 18129cba)
Signed-off-by: Steve Sakoman <steve@sakoman.com>