b: not exist
b/b.txt: not exist
Makefile:14: *** a exists in /home/kazubito/2010_11/autotest.mk/selftest/unittest/chk_file_ext.  中止.
Makefile:18: *** a/a.txt exists in /home/kazubito/2010_11/autotest.mk/selftest/unittest/chk_file_ext.  中止.