gmm::lapack_ipvt is a typedef to std::vector since 5.4.3 [1], so using
the .get() accessor no longer works. Removing the added CXXFLAGS fixes
the issue.
/wrkdirs/usr/ports/audio/csound/work/csound-6.15.0/Opcodes/linear_algebra.cpp:3507:30:
error: no member named 'get' in 'std::vector<unsigned long>'
3507 | pivot->vr[i] = pivot__.get(i);
[1] cbe1442c4b
Approved by: portmgr (blanket)