Fix false positive in config script check.

The new Config script finds and whines about MacGPG2.

I blanket whitelisted it because these are unrelated to the old errors
that MacGPG2 could cause.

This fixes the following false positives:
    /usr/local/MacGPG2/bin/gpg-error-config
    /usr/local/MacGPG2/bin/ksba-config
    /usr/local/MacGPG2/bin/libassuan-config
    /usr/local/MacGPG2/bin/libgcrypt-config
    /usr/local/MacGPG2/bin/libusb-config
    /usr/local/MacGPG2/bin/pth-config