lua-curl-v3 detects OS and changes compilation flags depends on OS.
If Darwin is detected then it adds GCC non-compatible flags.
OpenWrt is always Linux, OS detection is disabled via UNAME=Linux
as a part of MAKE_FLAGS

Signed-off-by: Sergey V. Lobanov <sergey@lobanov.in>

Signed-off-by: Rainer Poisel <rainer.poisel@gmail.com>