Go gcflags and ldflags can't be specified multiple times

[kirillx]

Most compilers like GCC would take multiple -ldflags arguments, and concatenate them to produce a list of additional arguments to ld.

go build is not doing so, and uses only the last -ldflags. Fortunately it is not completely that bad, and handles -ldflags ""
(an empty argument after -ldflags) as a no-op, so scripting is still possible.

So the proposal is to concatenate multiple gcflags/ldflags. If no objections - would provide PR.

What version of Go are you using (go version)?

$ go version
go version go1.17.1 darwin/amd64

Does this issue reproduce with the latest release?

yes

[mvdan]

Perhaps a duplicate of #38522?

[seankhliao]

Duplicate of #38522