gnutls: tweak postinstall

Since we’ve had to stick a temporary patch to OpenSSL’s postinstall
pending Apple’s response on the Equifax situation, GnuTLS which leans
on the OpenSSL formula to do postinstall is blowing up on every
Yosemite test-bot that calls GnuTLS as a dep.

```
==> Downloading
https://www.geotrust.com/resources/root_certificates/certificates/Equifa
x_Secure_Certificate_Authority.pem
Already downloaded:
/Library/Caches/Homebrew/openssl--Equifax_CA-Secure.pem
==> Verifying openssl--Equifax_CA-Secure.pem checksum
==> /usr/local/Cellar/openssl/1.0.2a-1/bin/c_rehash
Failed to execute: /usr/local/Cellar/openssl/1.0.2a-1/bin/c_rehash
Warning: The post-install step did not complete successfully
You can try again using `brew postinstall gnutls`
```

This works around that for now to stop the bot flagging failures
everywhere.

Closes #38619.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

0 files changed, 0 insertions, 0 deletions