removed lots of asserts

Some of them relied on the side effects of evaluating their argument but
for most of them it just makes more sense to use CHECK.
diff --git a/aos/common/libc/aos_strerror.cc b/aos/common/libc/aos_strerror.cc
index d5fc2b4..4bca500 100644
--- a/aos/common/libc/aos_strerror.cc
+++ b/aos/common/libc/aos_strerror.cc
@@ -26,7 +26,8 @@
 __attribute__((unused))
 char *aos_strerror_handle_result(int error, int ret, char *buffer) {
   if (ret != 0) {
-    assert(snprintf(buffer, kBufferSize, "Unknown error %d", error) > 0);
+    const int r = snprintf(buffer, kBufferSize, "Unknown error %d", error);
+    assert(r > 0);
   }
   return buffer;
 }