bytes: skip inline test by default

The test "TestTryGrowByResliceInlined" introduced in c08ac367 broke the
noopt builder as it fails when inlining is disabled.
Since there are currently no other options at hand for checking
inlined-ness other than looking at emited symbols of the compilation,
we for now skip the problem causing test by default and only run
it on one specific builder ("linux-amd64").
Also see CL 42813, which introduced the test and contains comments
suggesting this temporary solution.

Change-Id: I3978ab0831da04876cf873d78959f821c459282b
Reviewed-on: https://go-review.googlesource.com/42820Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/bytes/buffer_test.go

@@ -549,7 +549,12 @@ func TestBufferGrowth(t *testing.T) {
 }
 
 // Test that tryGrowByReslice is inlined.
+// Only execute on "linux-amd64" builder in order to avoid breakage.
 func TestTryGrowByResliceInlined(t *testing.T) {
+	targetBuilder := "linux-amd64"
+	if testenv.Builder() != targetBuilder {
+		t.Skipf("%q gets executed on %q builder only", t.Name(), targetBuilder)
+	}
 	t.Parallel()
 	goBin := testenv.GoToolPath(t)
 	out, err := exec.Command(goBin, "tool", "nm", goBin).CombinedOutput()