support/dependencies/dependencies.sh: silence gcc plugin test

The gcc plugin test was not using the -q option to grep causing it to print
the line to stdout, so fix that.

While we're at it, adjust the locale check to use grep -q instead of
redirecting to /dev/null for consistency with the other checks.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

support/dependencies/dependencies.sh

@@ -194,7 +194,7 @@ if [ "${PATCH_MAJOR}" -lt 2 ] || [ "${PATCH_MAJOR}" -eq 2 -a "${PATCH_MINOR}" -l
 	exit 1;
 fi
 
-if grep ^BR2_NEEDS_HOST_UTF8_LOCALE=y $BR2_CONFIG > /dev/null; then
+if grep -q ^BR2_NEEDS_HOST_UTF8_LOCALE=y $BR2_CONFIG ; then
 	if ! which locale > /dev/null ; then
 		echo
 		echo "You need locale support on your build machine to build a toolchain supporting locales"
@@ -254,7 +254,7 @@ if grep -q ^BR2_HOSTARCH_NEEDS_IA32_COMPILER=y $BR2_CONFIG ; then
 	fi
 fi
 
-if grep ^BR2_NEEDS_HOST_GCC_PLUGIN_SUPPORT=y $BR2_CONFIG ; then
+if grep -q ^BR2_NEEDS_HOST_GCC_PLUGIN_SUPPORT=y $BR2_CONFIG ; then
 	if ! echo "#include <gcc-plugin.h>" | $HOSTCXX_NOCCACHE -I$($HOSTCXX_NOCCACHE -print-file-name=plugin)/include -x c++ -c - -o /dev/null ; then
 		echo
 		echo "Your Buildroot configuration needs a host compiler capable of building gcc plugins."