This libgo patch makes runtime.Version return a meaningful string.
This also means that "go version" will print something useful, e.g.,

go version go1.18 gccgo (GCC) 12.0.1 20220216 (experimental) linux/amd64

This fixes https://go.dev/issue/51850.

Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian