This reverts commit 79af7fbf4ef0185fa501e23a900a2ad933f845a7.
Because:
* btashton reported some issues in local builds:
https://github.com/apache/incubator-nuttx/pull/603#issuecomment-602264860
* this might be related to the current CI breakage:
> /bin/sh: 1: /__w/incubator-nuttx/incubator-nuttx/nuttx/tools/mkdeps: not found
Squashed commit of the following:
libs/libxx: Fix some confusing in naming. If the directory is called libxx, then the library must be libxx.a (unless perhaps LIBCXX is selected).
libs/: Fix paths in moved library directories.
libs: Brute force move of libc, libnx, and libxx to libs. Cannot yet build it in that configuration.
