[release-branch.go1.10] cmd/go: skip TestVetWithOnlyCgoFiles when cgo is disabled
[release-branch.go1.10] cmd/go: skip TestVetWithOnlyCgoFiles when cgo is disabled

CL 99175 added TestVetWithOnlyCgoFiles. However, this
test is failing on platforms where cgo is disabled,
because no file can be built.

This change fixes TestVetWithOnlyCgoFiles by skipping
this test when cgo is disabled.

Fixes #24304.

Change-Id: Ibb38fcd3e0ed1a791782145d3f2866f12117c6fe
Reviewed-on: https://go-review.googlesource.com/99275
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
(cherry picked from commit b1335037fad4c81ce296f652372aa631a29dcb48)
Reviewed-on: https://go-review.googlesource.com/103223
Reviewed-by: David du Colombier <ec8ae1e6620d4bab5e0e7aa2a6ae41aad63e3708@gmail.com>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Run-TryBot: Andrew Bonventre <682ad9f487f614f19e8b7cc5d340bdc8e1c1b128@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

christopher-henderson/Go