build: Replace sed "s" command "i" flag

There's no such flag in standard sed.

1 files changed, 2 insertions, 1 deletions

diff --git a/build b/build
index 110c6ee..c53e1b2 100755
--- a/build
+++ b/build
@@ -1,6 +1,7 @@
 #! /usr/bin/make -f
 
-gcc_base_version = $$(sed 's/^GCC-Base-Version: //i' ../substvars)
+gcc_base_version = $$(tr '[:upper:]' '[:lower:]' <../substvars | \
+	sed 's/^gcc-base-version: //')
 
 build: