runtime: deflake TestNewOSProc0, fix _rt0_amd64_linux_lib stack alignment

This addresses iant's comments from CL 9164.

Change-Id: I7b5b282f61b11aab587402c2d302697e76666376
Reviewed-on: https://go-review.googlesource.com/9222Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/norace_linux_test.go

@@ -21,6 +21,8 @@ func newOSProcCreated() {
 	newOSProcDone = true
 }
 
+// Can't be run with -race because it inserts calls into newOSProcCreated()
+// that require a valid G/M.
 func TestNewOSProc0(t *testing.T) {
 	if runtime.GOOS == "android" && runtime.GOARCH == "arm" {
 		// newosproc0 does not work for android/arm.
@@ -28,10 +30,12 @@ func TestNewOSProc0(t *testing.T) {
 		t.Skipf("skipping on %v", runtime.GOOS)
 	}
 	runtime.NewOSProc0(0x800000, unsafe.Pointer(runtime.FuncPC(newOSProcCreated)))
-	check, end := time.Tick(1*time.Second), time.Tick(5*time.Second)
+	check := time.NewTicker(1 * time.Second)
+	defer check.Stop()
+	end := time.After(5 * time.Second)
 	for {
 		select {
-		case <-check:
+		case <-check.C:
 			if newOSProcDone {
 				return
 			}

src/runtime/rt0_linux_amd64.s

@@ -12,7 +12,7 @@ TEXT _rt0_amd64_linux(SB),NOSPLIT,$-8
 
 // When building with -buildmode=c-shared, this symbol is called when the shared
 // library is loaded.
-TEXT _rt0_amd64_linux_lib(SB),NOSPLIT,$0x40
+TEXT _rt0_amd64_linux_lib(SB),NOSPLIT,$0x48
 	MOVQ	BX, 0x10(SP)
 	MOVQ	BP, 0x18(SP)
 	MOVQ	R12, 0x20(SP)