In 20d2a30f8ffe (Makefile: replace perl/Makefile.PL with simple make
rules, 2017-12-10), Git stopped using MakeMaker. Therefore, that
definition in the MINGW-specific section became useless.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Reviewed-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>