JFTR: this bug has been fixed in the Automake-NG fork of Automake (which assumes GNU make is used to execute its generated makefiles); see commits v1.11-1838-gdc04691 "[ng] yacc, lex: fix subdir VPATH builds" and v1.11-1839-ge5b964c "[ng] yacc, lex, compiling: better use of '$<' (simplify and fix bug)" in the 'ng/master' branch of the official automake repository.
See also: <http://lists.gnu.org/archive/html/automake-ng/2012-02/msg00003.html> <http://lists.gnu.org/archive/html/automake-ng/2012-02/msg00011.html> More information about Automake-NG, from its first git commit: <http://lists.gnu.org/archive/html/automake-ng/2011-12/msg00000.html> Regards, Stefano
