[openwrt/openwrt] rules_mk: use gcc versions for external toolchain

[LEDE Commits]

ansuel pushed a commit to openwrt/openwrt.git, branch openwrt-21.02:
https://git.openwrt.org/56fd8355b078d8c9e1eb0bc0ea20900e7b46fe93

commit 56fd8355b078d8c9e1eb0bc0ea20900e7b46fe93
Author: Vincent Wiemann <vincent.wiemann at ironai.com>
AuthorDate: Mon Dec 28 16:00:13 2020 +0100

    rules_mk: use gcc versions for external toolchain
    
    When using the OpenWrt toolchain as an external toolchain the build
    failed due to missing LTO support. By choosing the GCC wrappers of
    the tools this commit makes sure that the LTO-enabled executables
    are being used.
    
    Signed-off-by: Vincent Wiemann <vincent.wiemann at ironai.com>
    [ wrap the commit description to 72 char ]
    Signed-off-by: Christian Marangi <ansuelsmth at gmail.com>
    (cherry picked from commit 2555ffb4536e2727465e9a0d426ad3c4f1ef003a)
---
 rules.mk | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/rules.mk b/rules.mk
index 9c694e17ce..631e07af00 100644
--- a/rules.mk
+++ b/rules.mk
@@ -245,20 +245,13 @@ HOST_CPPFLAGS:=-I$(STAGING_DIR_HOST)/include $(if $(IS_PACKAGE_BUILD),-I$(STAGIN
 HOST_CFLAGS:=-O2 $(HOST_CPPFLAGS)
 HOST_LDFLAGS:=-L$(STAGING_DIR_HOST)/lib $(if $(IS_PACKAGE_BUILD),-L$(STAGING_DIR_HOSTPKG)/lib -L$(STAGING_DIR)/host/lib)
 
-ifeq ($(CONFIG_EXTERNAL_TOOLCHAIN),)
-  TARGET_AR:=$(TARGET_CROSS)gcc-ar
-  TARGET_RANLIB:=$(TARGET_CROSS)gcc-ranlib
-  TARGET_NM:=$(TARGET_CROSS)gcc-nm
-else
-  TARGET_AR:=$(TARGET_CROSS)ar
-  TARGET_RANLIB:=$(TARGET_CROSS)ranlib
-  TARGET_NM:=$(TARGET_CROSS)nm
-endif
-
 BUILD_KEY=$(TOPDIR)/key-build
 
 FAKEROOT:=$(STAGING_DIR_HOST)/bin/fakeroot
 
+TARGET_AR:=$(TARGET_CROSS)gcc-ar
+TARGET_RANLIB:=$(TARGET_CROSS)gcc-ranlib
+TARGET_NM:=$(TARGET_CROSS)gcc-nm
 TARGET_CC:=$(TARGET_CROSS)gcc
 TARGET_CXX:=$(TARGET_CROSS)g++
 KPATCH:=$(SCRIPT_DIR)/patch-kernel.sh