runtime/pprof/internal/protopprof: skip TestTranslateCPUProfileWithSamples if < 2 mappings

A Go binary may only have 1 executable memory region if it has been
linked using internal linking. This change means that the test will
be skipped if this is the case, rather than fail.

Fixes #17852.

Change-Id: I59459a0f90ae8963aeb9908e5cb9fb64d7d0e0f4
Reviewed-on: https://go-review.googlesource.com/32920
Run-TryBot: Michael Munday <munday@ca.ibm.com>
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>

src/runtime/pprof/internal/protopprof/protopprof_test.go

@@ -162,7 +162,9 @@ func TestTranslateCPUProfileWithSamples(t *testing.T) {
 		t.Fatalf("Cannot parse /proc/self/maps")
 	}
 	if len(mprof.Mapping) < 2 {
-		t.Fatalf("Less than two mappings")
+		// It is possible for a binary to only have 1 executable
+		// region of memory.
+		t.Skipf("need 2 or more mappings, got %v", len(mprof.Mapping))
 	}
 	address1 := mprof.Mapping[0].Start
 	address2 := mprof.Mapping[1].Start