toolchain/gcc: use explicit configure args

Spell out what we want to enable or disable. This prevents host libs to leak in,
so everyone get the same feature set.

Signed-off-by: Andre Heider <a.heider@gmail.com>

toolchain/gcc/final/Makefile

@@ -8,6 +8,7 @@ GCC_CONFIGURE += \
 	--enable-shared \
 	--enable-threads \
 	--with-slibdir=$(TOOLCHAIN_DIR)/lib \
+	--enable-plugins \
 	--enable-lto \
 	--with-libelf=$(STAGING_DIR_HOST)