libmd: fix build with gcc

[barracuda156]

Closes: https://trac.macports.org/ticket/70706

Description

Fix build with gcc

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 10.6
Xcode 3.2

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint --nitpick?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?

[macportsbot]

Notifying maintainers:
@raimue for port libmd.

[raimue]

The port builds by default on all recent macOS versions. I do not feel comfortable to maintain such a patch locally in MacPorts without understanding the configuration under which it would be necessary.

Such a patch should also be submitted upstream first and be discussed there. A fix for the problem can be committed to the upstream source for the next release. Then this can be backported as a patch in MacPorts to fix the immediate build problem of the software in its current release.

[barracuda156]

@raimue I have attached log in the trac ticket.

For comparison, see: https://github.com/jpouellet/signify-osx/blob/master/hashaliases.c
This works fine, but the source of libmd uses something else instead, because it defines libmd_strong_alias.