Set stack_size from ulimit; set ulimit to 10000 in CI. (#687)

The goal of this change is to fix intermittent test failures we've started seeing
recently:

	=== RUN   TestMaxExecDepth
	FAIL	text/template	2.272s

In 1f89545, the --stack_size flag was
passed to Node.js. In nodejs/node#14567, it was pointed
out that the value of ulimit -s must be >= the value of --stack_size.

This change makes that so by setting --stack_size based on the current value
of ulimit, and sets ulimit to 10000 in CI.

circle.yml

@@ -20,7 +20,7 @@ test:
     - diff -u <(echo -n) <(go list ./compiler/natives/src/...) # All those packages should have // +build js.
     - gopherjs install -v net/http # Should build successfully (can't run tests, since only client is supported).
     - >
-      gopherjs test --minify -v --short
+      ulimit -s 10000 && gopherjs test --minify -v --short
       github.com/gopherjs/gopherjs/tests
       github.com/gopherjs/gopherjs/tests/main
       github.com/gopherjs/gopherjs/js

tool.go

@@ -750,9 +750,30 @@ func runNode(script string, args []string, dir string, quiet bool) error {
 	}
 
 	if runtime.GOOS != "windows" {
-		allArgs = append(allArgs, "--stack_size=10000", script)
+		// We've seen issues with stack space limits causing
+		// recursion-heavy standard library tests to fail (e.g., see
+		// https://github.com/gopherjs/gopherjs/pull/669#issuecomment-319319483).
+		//
+		// There are two separate limits in non-Windows environments:
+		//
+		// -	OS process limit
+		// -	Node.js (V8) limit
+		//
+		// GopherJS fetches the current OS process limit, and sets the
+		// Node.js limit to the same value. So both limits are kept in sync
+		// and can be controlled by setting OS process limit. E.g.:
+		//
+		// 	ulimit -s 10000 && gopherjs test
+		//
+		var r syscall.Rlimit
+		err := syscall.Getrlimit(syscall.RLIMIT_STACK, &r)
+		if err != nil {
+			return fmt.Errorf("failed to get stack size limit: %v", err)
+		}
+		allArgs = append(allArgs, fmt.Sprintf("--stack_size=%v", r.Cur/1000)) // Convert from bytes to KB.
 	}
 
+	allArgs = append(allArgs, script)
 	allArgs = append(allArgs, args...)
 
 	node := exec.Command("node", allArgs...)