While installing on OSX Sierra via gcc-6, keep having “FATAL:/opt/local/bin/../libexec/as/x86_64/as: I don't understand 'm' flag!” error

Question

Environment info

Operating System: macOS 10.12.2 (16C68)

Compiler: gcc-6

Steps to reproduce

I\'ve installed gcc-6 and modified config.mk

Answer 1

I solved by uninstalling MacPorts:

sudo port -f uninstall installed