* Posix BSP configuration: Moved some rules from make/custom/*-posix.cfg
files to make/custom/posix.cfg, Removed references to stdc++ from
*posix.cfg files (rtems doesn't use/need libstdc++)
NOTE: Building Posix-BSPs should now work again for native compilation with
gcc, i..e. linux using primary compiler and primary libc.
All Posix-BSP configurations that don't use gcc as primary compiler or
don't use the primary libc don't work, e.g. solaris, linux w/ egcs as
secondary compiler won't be built correctly.
0e70f60581