cmd/go: C compiler version parsing fails for versions like gcc 8.3 [DragonFly]

[bcmills]

Go version

c71eedf

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

dragonfly-amd64-622 at c71eedf90aff3fc73a645b88d2e5166b8a0179fd

:: Running /tmp/workdir/go/src/make.bash with args ["/tmp/workdir/go/src/make.bash" "-force"] and env ["PATH=/bin:/sbin:/usr/bin:/usr/local/bin" "HOME=/" "RC_PID=2" "WORKDIR=/tmp/workdir" "GOROOT_BOOTSTRAP=/tmp/workdir/go1.4" "GO_BUILDER_NAME=dragonfly-amd64-622" "GOBIN=" "TMPDIR=/tmp/workdir/tmp" "GOCACHE=/tmp/workdir/gocache" "GOPLSCACHE=/tmp/workdir/goplscache" "PWD=/tmp/workdir/go/src"] in dir /tmp/workdir/go/src

What did you do?

https://build.golang.org/log/3c7d2464881aa6cd4c5bec97b0fd3d3fc1addfa6

What did you expect to see?

All tests passing.

What did you see instead?

--- FAIL: TestScript (0.06s)
    --- FAIL: TestScript/cgo_stale_precompiled (0.92s)
        script_test.go:132: 2023-12-07T19:32:46Z
        script_test.go:134: $WORK=/tmp/workdir/tmp/cmd-go-test-6569609340248629423/tmpdir16117836249475985879/cgo_stale_precompiled1804669140117065298
        script_test.go:156: 
            # Regression test for https://go.dev/issue/47215 and https://go.dev/issue/50183:
            # A mismatched $GOROOT_FINAL or missing $CC caused the C dependencies of the net
            # package to appear stale, and it could not be rebuilt due to a missing $CC. (0.000s)
            # This test may start with the runtime/cgo package already stale.
            # Explicitly rebuild it to ensure that it is cached.
            # (See https://go.dev/issue/50892.)
            #
            # If running in non-short mode, explicitly vary CGO_CFLAGS
            # as a control case (to ensure that our regexps do catch rebuilds). (0.403s)
            # https://go.dev/issue/50183: a mismatched GOROOT_FINAL caused net to be stale. (0.193s)
            # https://go.dev/issue/47215: a missing $(go env CC) caused the precompiled net
            # to be stale. But as of https://go.dev/cl/452457 the precompiled libraries are
            # no longer installed anyway! Since we're requiring a C compiler in order to
            # build and use cgo libraries in the standard library, we should make sure it
            # matches what's in the cache. (0.311s)
            > [abscc] stop
            [condition not met]
            > env CGO_ENABLED=1
            > env CC=''
            > [!GOOS:plan9] env PATH=''  # Guaranteed not to include $(go env CC)!
            > [GOOS:plan9] env path=''
            [condition not met]
            > ! go build -x runtime/cgo
            [stderr]
            WORK=/tmp/workdir/tmp/cmd-go-test-6569609340248629423/tmpdir16117836249475985879/cgo_stale_precompiled1804669140117065298/tmp/go-build11950041837148003209
        script_test.go:156: FAIL: testdata/script/cgo_stale_precompiled.txt:39: go build -x runtime/cgo: unexpected success
FAIL
FAIL	cmd/go	52.660s

[gopherbot]

Change https://go.dev/cl/548120 mentions this issue: cmd/go: relax version regexp from CL 547998