--- ed-1.15/configure.old	2021-08-10 00:18:06.612959086 +0800
+++ ed-1.15/configure	2021-08-10 00:18:31.035115395 +0800
@@ -19,14 +19,14 @@
 bindir='$(exec_prefix)/bin'
 datarootdir='$(prefix)/share'
 infodir='$(datarootdir)/info'
 mandir='$(datarootdir)/man'
 program_prefix=
-CC=gcc
-CPPFLAGS=
-CFLAGS='-Wall -W -O2'
-LDFLAGS=
+CC=${CC-gcc}
+CPPFLAGS=${CPPFLAGS-}
+CFLAGS=${CFLAGS-"-Wall -W -O2"}
+LDFLAGS=${LDFLAGS-}
 
 # checking whether we are using GNU C.
 /bin/sh -c "${CC} --version" > /dev/null 2>&1 ||
 	{
 	CC=cc