Patch contains 2 changes:
- enable readline on FreeBSD (upstream never accepted this PR)
- use -O3 on FreeBSD

--- Makefile.orig	2023-01-10 11:11:11 UTC
+++ Makefile
@@ -4,7 +4,8 @@
 
 default: build/debug/mujs build/debug/mujs-pp
 
-CFLAGS = -std=c99 -pedantic -Wall -Wextra -Wno-unused-parameter
+# change to c11 on FreeBSD because FreeBSD headers induce c11 through isnan(3), etc.
+CFLAGS = -std=c11 -pedantic -Wall -Wextra -Wno-unused-parameter
 
 OPTIM = -O3
 
@@ -79,7 +80,7 @@ build/sanitize/mujs: main.c one.c $(SRCS) $(HDRS)
 
 build/debug/libmujs.$(SO): one.c $(SRCS) $(HDRS)
 	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) -g -fPIC -shared -o $@ one.c -lm
+	$(CC) $(CFLAGS) -g -fPIC -shared $(LDFLAGS) -o $@ one.c -lm
 build/debug/libmujs.o: one.c $(SRCS) $(HDRS)
 	@mkdir -p $(@D)
 	$(CC) $(CFLAGS) -g -c -o $@ one.c
@@ -92,7 +93,7 @@ build/debug/mujs-pp: pp.c build/debug/libmujs.o
 
 build/release/libmujs.$(SO): one.c $(SRCS) $(HDRS)
 	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(OPTIM) -fPIC -shared -o $@ one.c -lm
+	$(CC) $(CFLAGS) $(OPTIM) -fPIC -shared $(LDFLAGS) -o $@ one.c -lm
 build/release/libmujs.o: one.c $(SRCS) $(HDRS)
 	@mkdir -p $(@D)
 	$(CC) $(CFLAGS) $(OPTIM) -c -o $@ one.c