utils/mkdir-p: check if dir exists also after mkdir failed
utils/mkdir-p: check if dir exists also after mkdir failed

with "make install -j8" it happens very often that two or more make
instances are creating the same directory in parallel. As a result one
instace creates the directory and second mkdir fails because the
directory exists already (but it did not while testing for it earlier).

Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>

Reviewed-by: Matt Caswell <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@openssl.org>
Reviewed-by: Rich Salz <c04971a99e5a9ee80eaab4b1deb37e845b0bd697@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1204)
openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl