fixed lots of not-thread-safe things
Most of the things I fixed here were using libc functions that are
fundamentally not thread-safe.
diff --git a/aos/common/util/run_command.h b/aos/common/util/run_command.h
new file mode 100644
index 0000000..d116481
--- /dev/null
+++ b/aos/common/util/run_command.h
@@ -0,0 +1,17 @@
+#ifndef AOS_COMMON_UTIL_RUN_COMMAND_H_
+#define AOS_COMMON_UTIL_RUN_COMMAND_H_
+
+namespace aos {
+namespace util {
+
+// Improved replacement for system(3). Doesn't block signals like system(3) and
+// is thread-safe. Also makes sure all 3 standard streams are /dev/null.
+//
+// This means that it passes command to `/bin/sh -c` and returns -1 or a status
+// like from wait(2).
+int RunCommand(const char *command);
+
+} // namespace util
+} // namespace aos
+
+#endif // AOS_COMMON_UTIL_RUN_COMMAND_H_