cmd/dist: GOARM inference fails with arm64 kernel

[mwhudson]

This is a selfish bug report: the fastest and most reliable 32-bit arm environment I have access to is a armhf chroot on an arm64 system and currently I'm fairly sure it falls back to GOARM=5 when running ./all.bash. I think checking assuming GOARM=7 when uname -m == armv8l would be appropriate.

[bradfitz]

Sounds fine.

[minux]

Could we reconsider restoring the automatic detection feature? CL 3973.

[bradfitz]

The build is slow enough. I don't want to see it compiling and running a program for a simple check.

Can you modify CL 3973 to make it compile those two probe functions into the dist binary itself, and then just make dist exec its own binary (argv[0]) as a child to do the probe and see whether it crashes? It would at least eliminate the extra compile and disk I/O.

[gopherbot]

CL https://golang.org/cl/14413 mentions this issue.

[minux]

I will update CL 3973 to do the re-exec itself trick. I didn't do it before because I was concerned that os.Args[0] might not be pointing to the program, and we don't have a portable way to get the current process' executable path.

[gopherbot]

CL https://golang.org/cl/3973 mentions this issue.

[mwhudson]

Minux's CL fixed this.