cmd/compile: fix heap dump test on android

go_android_exec is looking for "exitcode=" to decide the result
of running a test.  The heap dump test nondeterministically prints
"finalized" right at the end of the test.  When the timing is just
right, we print "finalizedexitcode=0" and confuse go_android_exec.

This failure happens occasionally on the android builders.

Change-Id: I4f73a4db05d8f40047ecd3ef3a881a4ae3741e26
Reviewed-on: https://go-review.googlesource.com/23861
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

src/runtime/debug/heapdump_test.go

@@ -38,7 +38,7 @@ type Obj struct {
 }
 
 func objfin(x *Obj) {
-	println("finalized", x)
+	//println("finalized", x)
 }
 
 func TestWriteHeapDumpFinalizers(t *testing.T) {