cmd/go: with -compiler=gccgo, only call runtime.setmodinfo if using a version of gccgo that supports it

What version of Go are you using (go version)?

Does this issue reproduce with the latest release?

No. It is on tip only.

$ gccgo --version
gccgo (Debian 8.3.0-6) 8.3.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE

What operating system and processor architecture are you using (go env)?

What did you do?

go run -compiler=gccgo example.go

What did you expect to see?

Normal run.

What did you see instead?

# command-line-arguments
/usr/bin/ld: $WORK/b001/_pkg_.a(_go_.o): in function `main.main..init0':
/tmp/go-build/b001/_gomod_.go:5: undefined reference to `runtime.setmodinfo

It is on Debian 10 stable.