[release-branch.go1.4] cmd/go: if -no-pie doesn't work, try -nopie

This is a backport of https://golang.org/cl/49710 to the Go 1.4 branch.

Original CL description:
    GCC says -no-pie, clang says -nopie.

Updates #21042

Change-Id: I67b755ccb0149324098b79e07ee4bbc49429c44c
Reviewed-on: https://go-review.googlesource.com/49711


Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>