cmd/dist: log CPU model when testing

Knowing whether test failures are correlated with specific CPU models on
has proven useful on several issues. Log it for prior to testing so it
is always available.

internal/sysinfo provides the CPU model, but it is not available in the
bootstrap toolchain, so we can't access this unconditionally in
cmd/dist. Instead use a build-tagged file, as the final version of
cmd/dist will use the final toolchain.

The addition of new data to the beginning of cmd/dist output will break
x/build/cmd/coordinator's banner parsing, leaving extra lines in the log
output, though information will not be lost.
https://golang.org/cl/372538 fixes up the coordinator and should be
submitted and deployed before this CL is submitted.

For #46272.
For #49209.
For #50146.

Change-Id: I515d2ec58e4c0034b76bf624ecaab38f16146074
Reviewed-on: https://go-review.googlesource.com/c/go/+/371474
Trust: Benny Siegert <bsiegert@gmail.com>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
Trust: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/src/cmd/dist/metadata_bootstrap.go b/src/cmd/dist/metadata_bootstrap.go
new file mode 100644
index 00000000000..fe5f422b0b9
--- /dev/null
+++ b/src/cmd/dist/metadata_bootstrap.go
@@ -0,0 +1,21 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// No-op metadata implementation when building with an old bootstrap toolchain.
+
+//go:build !go1.18
+// +build !go1.18
+
+package main
+
+import (
+	"fmt"
+)
+
+func logMetadata() error {
+	// We don't return an error so we don't completely preclude running
+	// tests with a bootstrap dist.
+	fmt.Printf("# Metadata unavailable: bootstrap build\n")
+	return nil
+}