g: SRC_ROOT may not contain path string in a localized environment

When config_host.mk contains non-ascii characters(e.g. Japanese ),
SRC_ROOT may contain an error message "Binary file (standard input)
 matches") from grep, and SRC_ROOT may not contain path string.
With '-a' option, grep will work well.

Change-Id: Ifaada5f5a11939d624460cd8dcc57d93911ae790
Reviewed-on: https://gerrit.libreoffice.org/14491Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

g

@@ -12,7 +12,7 @@ SUBMODULES_ALL="dictionaries helpcontent2 translations"
 pushd $(dirname $0) > /dev/null
 if [ -f config_host.mk ] ; then
     # we are in the BUILDDIR
-    SRC_ROOT=$(cat config_host.mk | grep SRC_ROOT | sed -e "s/.*=//")
+    SRC_ROOT=$(cat config_host.mk | grep -a SRC_ROOT | sed -e "s/.*=//")
 else
     SRC_ROOT=$(pwd)
 fi