cmd/go/testdata/script: fix test failing on nocgo builders
cmd/go/testdata/script: fix test failing on nocgo builders

The regression test introduced in https://golang.org/cl/318770 broke the
the nocgo builders.

Update the cgo package used in the test to ensure that it can be build
both with cgo enabled and disabled.

Change-Id: Iab0486f0b85ac5e5a22fdf8a1998edd50cbb4d96
Reviewed-on: https://go-review.googlesource.com/c/go/+/319210
Trust: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Trust: Jay Conrod <f3fadaedc813344da5ec13b41e26596889cc5baa@google.com>
Reviewed-by: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Reviewed-by: Jay Conrod <f3fadaedc813344da5ec13b41e26596889cc5baa@google.com>
Run-TryBot: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

nawawi/go,cloudflare/go,golang/go,nawawi/go,golang/go,CAFxX/go,golang/go,CAFxX/go,cloudflare/go,golang/go,cloudflare/go,nawawi/go,CAFxX/go,nawawi/go,nawawi/go,cloudflare/go,nawawi/go,cloudflare/go,CAFxX/go,nawawi/go,CAFxX/go,golang/go,nawawi/go,golang/go,CAFxX/go,cloudflare/go,golang/go,golang/go,CAFxX/go,CAFxX/go,cloudflare/go,cloudflare/go