cmd/vendor/github.com/google/pprof: cherry-pick fix to cope with $HOME not being writable

Upstream PRs: https://github.com/google/pprof/pull/305,
https://github.com/google/pprof/pull/306.

Change-Id: I28969118f52ee08fcaf3572ad5da015ae756fd7a
Reviewed-on: https://go-review.googlesource.com/90935
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/vendor/github.com/google/pprof/internal/driver/fetch_test.go

@@ -362,6 +362,18 @@ func TestHttpsInsecure(t *testing.T) {
 	if runtime.GOOS == "nacl" {
 		t.Skip("test assumes tcp available")
 	}
+	saveHome := os.Getenv(homeEnv())
+	tempdir, err := ioutil.TempDir("", "home")
+	if err != nil {
+		t.Fatal("creating temp dir: ", err)
+	}
+	defer os.RemoveAll(tempdir)
+
+	// pprof writes to $HOME/pprof by default which is not necessarily
+	// writeable (e.g. on a Debian buildd) so set $HOME to something we
+	// know we can write to for the duration of the test.
+	os.Setenv(homeEnv(), tempdir)
+	defer os.Setenv(homeEnv(), saveHome)
 
 	baseVars := pprofVariables
 	pprofVariables = baseVars.makeCopy()