all: skip more memory-intensive tests on linux-arm

Updates golang/go#32834

Change-Id: I9844dc09d9a6eb2e79a0b28a1e69ed018bfa1bff
Reviewed-on: https://go-review.googlesource.com/c/tools/+/192578
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Author: Bryan C. Mills

internal/testenv/testenv.go

@@ -7,6 +7,7 @@
 package testenv
 
 import (
+	"fmt"
 	"os"
 	"os/exec"
 	"runtime"
@@ -106,3 +107,14 @@ func NeedsGoPackagesEnv(t Testing, env []string) {
 
 	NeedsGoPackages(t)
 }
+
+// ExitIfSmallMachine emits a helpful diagnostic and calls os.Exit(0) if the
+// current machine is a builder known to have scarce resources.
+//
+// It should be called from within a TestMain function.
+func ExitIfSmallMachine() {
+	if os.Getenv("GO_BUILDER_NAME") == "linux-arm" {
+		fmt.Fprintln(os.Stderr, "skipping test: linux-arm builder lacks sufficient memory (https://golang.org/issue/32834)")
+		os.Exit(0)
+	}
+}