as in summary: gmt-4.5.9 fails to build, while it should do.
Created attachment 429402 [details]
Created attachment 429404 [details]
the headline should be changed to:
sci-geosciences/gmt-4.5.6[mex] - make: /usr/bin/mex: Command not found
w/o the "mex" USE flag it compiles fine on my system