Author: Patrick McDermott <patrick.mcdermott@libiquity.com>
Subject: Use non-POSIX sed -r

BusyBox didn't support the POSIX -E option until version 1.22.0.

diff -Naurp src.orig/scripts/headers_install.sh src/scripts/headers_install.sh
--- src.orig/scripts/headers_install.sh	2019-06-24 23:36:02.000000000 -0400
+++ src/scripts/headers_install.sh	2019-07-10 19:52:42.152146074 -0400
@@ -31,7 +31,7 @@ trap 'rm -f "$OUTDIR/$FILE" "$OUTDIR/$FI
 for i in "$@"
 do
 	FILE="$(basename "$i")"
-	sed -E \
+	sed -r \
 		-e 's/([[:space:](])(__user|__force|__iomem)[[:space:]]/\1/g' \
 		-e 's/__attribute_const__([[:space:]]|$)/\1/g' \
 		-e 's@^#include <linux/compiler(|_types).h>@@' \