in tools/Makefile.gnuhost. This makes the tools version of m4
behave like GNU m4.
Remove similar code from tools/autoconf/Makefile, where it didn't
work because Makefile.gnuhost would previously have overridden it.
This fixes a problem in which the tools version of autoconf complained
"M4sugar requires GNU M4.
Install it before installing M4sugar or set the M4 environment variable to its path name."