MFH: r523016
math/gau2grid: remove -march=native, unbreak on i386 and powerpc64
This port added -march=native, which was against ports tree compliance, broke run-time on some amd64 and broke building on non-x86.
I have verified that it builds correctly on i386 and powerpc64 (provided -march=native is removed). It probably also builds on other architectures.
Reviewed by: linimon
Approved by: portmgr (fix build blanket)