[MDC-434] simetbox-openwrt-simet-lmapd: OpenWRT Chaos Calmer compatib…

[MDC-434] simetbox-openwrt-simet-lmapd: OpenWRT Chaos Calmer compatibility

* Add a nasty hack to patch in CMake 2.8.12 compatibility for OpenWRT
  CC builds.  The hack has to run on OpenWRT CC, so we have to use
  PKG_BUILD_DIR, because CMAKE_SOURCE_DIR will be "./" or something
  equally broken.

* Work around the lack of O_CLOEXEC for open() in uClibc