[release-branch.go1.21 cmd/cgo/internal/test: don't pass -lm on darwin
On darwin, -lm is not necessary as the math functions are included
in libSystem. Passing -lm multiple times results in linker
warnings. Don't pass it on darwin.
For #61229.
Change-Id: I72d8dab1f0eead68cbeb176ac97b8ed1a0cfddab
Reviewed-on: https://go-review.googlesource.com/c/go/+/508697
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
(cherry picked from commit
333c80694c797b5540c959f33c710bc6eba0d141)
Reviewed-on: https://go-review.googlesource.com/c/go/+/513758