--- core/Makefile.orig	2020-06-20 10:41:54.000000000 -0400
+++ core/Makefile	2020-06-20 10:50:49.000000000 -0400
@@ -1,8 +1,8 @@
-PREFIX = /usr/local
-LIBDIR = $(PREFIX)/libexec/mafft
-BINDIR = $(PREFIX)/bin
-MANDIR = $(PREFIX)/share/man/man1
-DESTDIR = 
+PREFIX ?= /usr/local
+LIBDIR ?= $(PREFIX)/libexec/mafft
+BINDIR ?= $(PREFIX)/bin
+MANDIR ?= $(PREFIX)/share/man/man1
+DESTDIR ?= 
 
 #MNO_CYGWIN = -mno-cygwin
 
@@ -18,9 +18,9 @@
 # Uncomment the above line to use protein 3D 
 # structural information.  Go language is required.
 
-CC = gcc
+CC ?= gcc
 #CC = icc
-CFLAGS = -O3
+#CFLAGS = -O3
 #CFLAGS = -O3 -fPIC
 # add -fPIC when building .so files