glib2 @2.56.2: won't build +universal if libgcc7 installed

[kencu (Ken)]

This is a niche situation, admittedly, disappearing from MacPorts.

building glib2 +universal fails on Tiger (and presumably Leopard) if libgcc7 is installed and active.

configuration of glib2 fails when it tries to find a compatible iconv_open to use. It finds /opt/local/lib/libstdc++.6.dylib installed by libgcc7 which is only built in the host architecture, and errors out.

However, if libgcc7 is deactivated, then configure finds /usr/lib/libstdc++.6.dylib instead, which is multiarchitecture and fat, and the universal build succeeds without issue.

I'm not sure if glib2 can be set up to find /usr/lib/libstdc++.6.dylib preferentially. In the meantime, deactivating libgcc7, upgrading glib2, and then reactivating libgcc7 is a fairly trivial workaround.