makeparallel: reset make's unlimited stack

make 3.81 sets its own stack size to be unlimited, but accidentally
leaves it unlimited for all child processes.  If it is unlimited, reset
it back to a reasonable default (8MB).

See http://savannah.gnu.org/bugs/?22010

Change-Id: Ieb0289823f12a421b59d8ab5292d3df3c6dfc27e
diff --git a/tools/makeparallel/makeparallel.cpp b/tools/makeparallel/makeparallel.cpp
index 3c39846..c70fa9a 100644
--- a/tools/makeparallel/makeparallel.cpp
+++ b/tools/makeparallel/makeparallel.cpp
@@ -26,6 +26,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <sys/resource.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <sys/wait.h>
@@ -343,6 +344,15 @@
     // child
     unsetenv("MAKEFLAGS");
     unsetenv("MAKELEVEL");
+
+    // make 3.81 sets the stack ulimit to unlimited, which may cause problems
+    // for child processes
+    struct rlimit rlim{};
+    if (getrlimit(RLIMIT_STACK, &rlim) == 0 && rlim.rlim_cur == RLIM_INFINITY) {
+      rlim.rlim_cur = 8*1024*1024;
+      setrlimit(RLIMIT_STACK, &rlim);
+    }
+
     int ret = execvp(path, args.data());
     if (ret < 0) {
       error(errno, errno, "exec %s failed", path);