vim: do not adjust script paths building for target

When cross-compiling, do not change scripts to use host
versions of perl and gawk.

Also, use INSANE_SKIP to suppress QA complaints if perl
or gawk are not on the target.

Signed-off-by: Joe Slater <joe.slater@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>