[gimp] build: Improve BOM-adding on InnoSetup files.

[Jehan <jehanp src gnome org>]

commit 9ba44aab2ad0350de5277bfff8f6da79a65c707f
Author: Jehan <jehan girinstud io>
Date:   Mon Jan 10 21:27:12 2022 +0100

    build: Improve BOM-adding on InnoSetup files.
    
    My previous command was also adding a linefeed just after the BOM. While
    I'm not sure it would really break anything for processing these, it's
    anyway much more correct to only add the 3 BOM bytes. So here is the
    improved command.

 build/windows/gitlab-ci/installer-gimp-msys2.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/build/windows/gitlab-ci/installer-gimp-msys2.sh b/build/windows/gitlab-ci/installer-gimp-msys2.sh
index 483798ad6a..6f5b9cb872 100644
--- a/build/windows/gitlab-ci/installer-gimp-msys2.sh
+++ b/build/windows/gitlab-ci/installer-gimp-msys2.sh
@@ -33,7 +33,7 @@ add_bom ()
   file "$lang.isl" |grep "with BOM" 2>&1 > /dev/null
   has_bom="$?"
   if [ $has_bom -ne 0 ]; then
-    sed -i "1 i \\\xEF\xBB\xBF" "$lang.isl"
+    sed -i "1s/^/\xEF\xBB\xBF/" "$lang.isl"
   fi
 }