gdb: support external toolchain

toolchain/gdb/gdb.mk

@@ -20,21 +20,17 @@ GDB_DIR:=$(TOOL_BUILD_DIR)/gdb-$(GDB_VERSION)
 GDB_PATCH_DIR:=toolchain/gdb/$(GDB_VERSION)
 else
 
-ifeq ($(BR2_TOOLCHAIN_BUILDROOT),y)
-GDB_SITE:=$(BR2_GNU_MIRROR)/gdb
-else
-GDB_SITE:=$(VENDOR_SITE)
-endif
-
 GDB_OFFICIAL_VERSION:=$(GDB_VERSION)$(VENDOR_SUFFIX)$(VENDOR_GDB_RELEASE)
 
 GDB_SOURCE:=gdb-$(GDB_OFFICIAL_VERSION).tar.bz2
 GDB_CAT:=$(BZCAT)
 
-ifeq ($(BR2_TOOLCHAIN_BUILDROOT),y)
-GDB_PATCH_DIR:=toolchain/gdb/$(GDB_OFFICIAL_VERSION)
-else
+ifeq ($(BR2_TOOLCHAIN_EXTERNAL_SOURCE),y)
+GDB_SITE:=$(VENDOR_SITE)
 GDB_PATCH_DIR:=$(VENDOR_PATCH_DIR)/gdb-$(GDB_OFFICIAL_VERSION)
+else
+GDB_SITE:=$(BR2_GNU_MIRROR)/gdb
+GDB_PATCH_DIR:=toolchain/gdb/$(GDB_OFFICIAL_VERSION)
 endif
 
 GDB_DIR:=$(TOOL_BUILD_DIR)/gdb-$(GDB_OFFICIAL_VERSION)