--- mk/elftoolchain.prog.mk.orig	2017-06-11 16:21:28.000000000 +0200
+++ mk/elftoolchain.prog.mk	2017-06-11 16:21:47.000000000 +0200
--- mk/os.Darwin.mk	(revision 3546)
+++ mk/os.Darwin.mk	(working copy)
@@ -3,6 +3,5 @@
 # Build definitions for Darwin
 
 # Apple ships libarchive, but for some reason does not provide the headers.
-# Build against a homebrew-provided libarchive library and headers.
-LDFLAGS+=	-L/usr/local/opt/libarchive/lib
-CFLAGS+=	-I/usr/local/opt/libarchive/include
+# Build against a MacPorts-provided libarchive library and headers.
+# LDFLAGS/CFLAGS for libarchive have to be set in the environment.