Remove some hardcoded optimization/warnings flags.  This will become obsolete
with the next release.

--- Makefile.orig	2020-12-26 22:51:37 UTC
+++ Makefile
@@ -9,8 +9,8 @@ endif
 
 CC=gcc
 CFLAGS0:=$(CFLAGS)
-CFLAGS+=-I. -Wall -W -Wno-implicit-fallthrough -Wno-format-truncation \
--Wno-stringop-overflow -O3 -fsigned-char
+CFLAGS+=-I. -Wall -W -Wno-implicit-fallthrough \
+-fsigned-char
 # Enable -Wstringop-overflow[=type] when it is no longer a broken, partial
 # implementation with false positives for trivial cases.
 LDFLAGS0:=$(LDFLAGS)