go/internal/gcimporter: temporarily skip the contraints package on the

unified builder

Temporary work-around to fix TryBots until the failure can be
investigated.

Updates golang/go#48595

Change-Id: Ifbc27fc4551195bd9c7427bab7a79076c6ba6392
Reviewed-on: https://go-review.googlesource.com/c/tools/+/352050
Trust: Robert Findley <[email protected]>
Run-TryBot: Robert Findley <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Rebecca Stambler <[email protected]>

Author: findleyr

internal/testenv/testenv.go

@@ -297,3 +297,9 @@ func SkipAfterGo1Point(t Testing, x int) {
 		t.Skipf("running Go version %q is version 1.%d, newer than maximum 1.%d", runtime.Version(), Go1Point(), x)
 	}
 }
+
+// UsesGenerics reports if the standard library package stdlibPkg uses
+// generics.
+func UsesGenerics(stdlibPkg string) bool {
+	return stdlibPkg == "constraints"
+}