as in summary: gmt-4.5.9 fails to build, while it should do.
Created attachment 429402 [details] emerge --info
Created attachment 429404 [details] build log
the headline should be changed to: sci-geosciences/gmt-4.5.6[mex] - make[2]: /usr/bin/mex: Command not found w/o the "mex" USE flag it compiles fine on my system