Build unix_dir for NaCl.

There are several functions in the 'unix' subfolder which
we currently ship headers for, but not implementions. e.g
dirname(3) and basename(3).

This change adds the 'unix' directory to the NaCl build
of newlib and excludes the 4 functions which don't
currently compile.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3651
TEST= pnacl/build.sh
R=mcgrathr@chromium.org

Review URL: https://codereview.chromium.org/23470002
1 file changed