This patch is based on the following upstream patch
From 0027b072627aa9d3ada71c4374561966064ecd5a Mon Sep 17 00:00:00 2001
From: "M. Herdiansyah"
Date: Thu, 11 Jun 2020 19:40:24 +0700
Subject: [PATCH] Makefile: increase compatibility with bmake (#551)
--- Makefile.in.orig	2020-07-04 16:53:39 UTC
+++ Makefile.in
@@ -2012,7 +2012,7 @@ uninstall-am: uninstall-pkgconfigDATA uninstall-toolex
 @LIBFFI_BUILD_VERSIONED_SHLIB_SUN_TRUE@@LIBFFI_BUILD_VERSIONED_SHLIB_TRUE@	 > $@ || (rm -f $@ ; exit 1)
 
 libffi.map: $(top_srcdir)/libffi.map.in
-	$(COMPILE) -D$(TARGET) -E -x assembler-with-cpp -o $@ $<
+	$(COMPILE) -D$(TARGET) -E -x assembler-with-cpp -o $@ $(top_srcdir)/libffi.map.in
 
 dist-hook:
 	d=`(cd $(distdir); pwd)`; (cd doc; make pdf; cp *.pdf $$d/doc)