cmd/go: go build should honor umask

[0xmohit]

No matter what the umask, go build would always create a binary with perms 0755.

$  ( umask 0022; go build -o foo foo.go ; ls -l foo )
-rwxr-xr-x 1 ubuntu ubuntu 2848496 Sep 19 12:00 foo
$  ( umask 0000; go build -o foo foo.go ; ls -l foo )
-rwxr-xr-x 1 ubuntu ubuntu 2848496 Sep 19 12:00 foo
$  ( umask 0077; go build -o foo foo.go ; ls -l foo )
-rwxr-xr-x 1 ubuntu ubuntu 2848496 Sep 19 12:00 foo

Compilers (including gcc, ghc, dmd) usually respect umask while creating executables.

[ianlancetaylor]

I think this happens because moveOrCopyFile in cmd/go/build.go calls os.Chmod without considering umask.

[AndersKOlsson]

+1. This is really irritating, for example when building through the golang Docker image, and ending up with root owned, undeletable files on the host.

[gopherbot]

CL https://golang.org/cl/17950 mentions this issue.