Give batch files CRLF line endings

Batch files should be CRLF, otherwise they may end up triggering an
"The system cannot find the batch label specified" error.

Relying on core.autocrlf to ensure this runs the risk of the user not
having the config set correctly, and also doesn't cover the use of
the same source checkouts across platforms.

Change-Id: I3166b99ce38e4ba9a0674336d69aa915e27860d1
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>

.gitattributes

@@ -2,3 +2,5 @@
 .gitignore              export-ignore
 .gitattributes          export-ignore
 .commit-template        export-ignore
+*.bat                   text eol=crlf
+*.bat.in                text eol=crlf