build: use new toolchain variables for tools

This change migrates the values of `CC`, `CPP`, `AS` and other toolchain
variables to the new `$(toolchain)-$(tool)` variables, which were
introduced by the toolchain refactor patch. These variables should be
equivalent to the values that they're replacing.

Change-Id: I644fe4ce82ef1894bed129ddb4b6ab94fb04985d
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/plat/nvidia/tegra/platform.mk b/plat/nvidia/tegra/platform.mk
index 2365564..0221b5e 100644
--- a/plat/nvidia/tegra/platform.mk
+++ b/plat/nvidia/tegra/platform.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2015-2024, Arm Limited and Contributors. All rights reserved.
 # Copyright (c) 2020, NVIDIA Corporation. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
@@ -82,7 +82,7 @@
 INCLUDES	+=	-Iinclude/lib/libc		\
 			-Iinclude/lib/libc/$(ARCH)	\
 
-ifneq ($(findstring armlink,$(notdir $(LD))),)
+ifneq ($(findstring armlink,$(notdir $($(ARCH)-ld))),)
 # o suppress warnings for section mismatches, undefined symbols
 # o use only those libraries that are specified in the input file
 #   list to resolve references