cmd/cgo: remove hardcoded '-pie' ldflag for linux/arm

a minimally invasive fix proposal for #45940. which keeps the fix for #26197.

an alternative for (#26197) could be to fail if we have both flags. adding/removing a flag without an message to the user is inconvenient.

Change-Id: I6ac2524d81ff57202fbe3032a53afd5106270a9e
GitHub-Last-Rev: edaf02fa455329b5d794a139f99874b5e8cc12d1
GitHub-Pull-Request: golang/go#45989
Reviewed-on: https://go-review.googlesource.com/c/go/+/317569


Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Bryan C. Mills <bcmills@google.com>