cmd/dist: add serial/small build option for GOMAXPROCS=1

If GOMAXPROCS=1, force serial execution, which is better for
debugging build problems and also minimizes footprint, if that
happens to matter.

This wasn't good when the bootstrap was 1.4 because there
default GOMAXPROCS=1, but that is no longer the bootstrap
version.

Change-Id: I637e25c8acb4758795fceef63921eda359a7be29
Reviewed-on: https://go-review.googlesource.com/c/go/+/452556
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

diff --git a/src/cmd/dist/main.go b/src/cmd/dist/main.go
index 0dc409fc770537891eaad1258f1d38f84638d807..6194ea901c2dc792152da57f7b71ae2cead815da 100644 (file)
--- a/src/cmd/dist/main.go
+++ b/src/cmd/dist/main.go
@@ -159,6 +159,12 @@ func main() {
        if gohostarch == "arm" || gohostarch == "mips64" || gohostarch == "mips64le" {
                maxbg = min(maxbg, runtime.NumCPU())
        }
+       // For deterministic make.bash debugging and for smallest-possible footprint,
+       // pay attention to GOMAXPROCS=1.  This was a bad idea for 1.4 bootstrap, but
+       // the bootstrap version is now 1.17+ and thus this is fine.
+       if runtime.GOMAXPROCS(0) == 1 {
+               maxbg = 1
+       }
        bginit()
 
        if len(os.Args) > 1 && os.Args[1] == "-check-goarm" {