gmt5, gmt6: use github for tarball and livecheck

[remkos]

Description

This makes livecheck on gmt5 and gmt6 work and en passant changes to getting the tarball from github

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 10.15.2
Xcode Command Line tools 10.3

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?

• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?

[macportsbot]

Notifying maintainers:
@tenomoto for port gmt5.

[macportsbot]

Travis Build #9985 Errored.

Lint results

--->  Verifying Portfile for gmt5
--->  0 errors and 0 warnings found.

Port gmt5 success on xcode10.3. Log
Port gmt5 success on xcode9.4. Log
Port gmt6 success on xcode9.4. Log
Port gmt5 success on xcode8.3. Log
Port gmt6 success on xcode8.3. Log
Port gmt5 success on xcode7.3. Log
Port gmt6 success on xcode7.3. Log

The build timed out.

[g5pw]

This looks fine. Thanks for your contribution to MacPorts, @remkos, and sorry for the delay in merging this. Pinging macports-dev is the way to go if things get a little backed up.

[remkos]

This looks fine. Thanks for your contribution to MacPorts, @remkos, and sorry for the delay in merging this. Pinging macports-dev is the way to go if things get a little backed up.

Thanks, I'll do so next time.

[g5pw]

You already did! That's how I got the heads up that this still needed to be merged. :)