Allow user to override environment variables.
https://github.com/love2d/love/commit/e6f06fbc78e5b7194e6ff56594248ce3688487dc
--- platform/unix/automagic.orig	2012-04-02 15:31:32.000000000 -0500
+++ platform/unix/automagic	2024-05-05 21:22:41.000000000 -0500
@@ -5,11 +5,11 @@
 	exit 1
 }
 
-AUTOHEADER=$(which autoheader)
-AUTOCONF=$(which autoconf)
-LIBTOOLIZE=$(which libtoolize)
-ACLOCAL=$(which aclocal)
-AUTOMAKE=$(which automake)
+AUTOHEADER=${AUTOHEADER:-$(which autoheader)}
+AUTOCONF=${AUTOCONF:-$(which autoconf)}
+LIBTOOLIZE=${LIBTOOLIZE:-$(which libtoolize)}
+ACLOCAL=${ACLOCAL:-$(which aclocal)}
+AUTOMAKE=${AUTOMAKE:-$(which automake)}
 
 [[ -x ${AUTOHEADER} ]] || die "Could not find autoheader. Install autoconf."
 [[ -x ${AUTOCONF} ]]   || die "Could not find autoconf."