Makefile.common: eliminate LIBC_LIBRARY_OPTION
Makefile.common: eliminate LIBC_LIBRARY_OPTION

We can use -lc unconditionally; nano.specs will rewrite it to -lc_s or
-lc_nano depending on toolchain release.  Change supports 4_9-2014q4.

pabigot/bspacm,pabigot/bspacm,pabigot/bspacm,pabigot/bspacm