cmake: use ZEPHYR_SDK_INSTALL_DIR instead of TOOLCHAIN_HOME

Zephyr SDK specifies TOOLCHAIN_HOME in cmake/zephyr/generic.cmake for
use in Zephyr.

But when specifying Zephyr SDK contolled variables isuch as SYSROOT_DIR
or CROSS_COMPILE, then the Zephyr SDK should rightfully use
ZEPHYR_SDK_INSTALL_DIR instead.
The use of TOOLCHAIN_HOME stems from the time when the Zephyr SDK cmake
code was present in the Zephyr repo and not part of the Zephyr SDK
itself.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>

Author: tejlmand

cmake/zephyr/target.cmake

@@ -26,8 +26,8 @@ set(CROSS_COMPILE_TARGET_sparc     sparc-zephyr-elf)
 set(CROSS_COMPILE_TARGET ${CROSS_COMPILE_TARGET_${ARCH}})
 set(SYSROOT_TARGET       ${CROSS_COMPILE_TARGET})
 
-set(SYSROOT_DIR   ${TOOLCHAIN_HOME}/${SYSROOT_TARGET}/${SYSROOT_TARGET})
-set(CROSS_COMPILE ${TOOLCHAIN_HOME}/${CROSS_COMPILE_TARGET}/bin/${CROSS_COMPILE_TARGET}-)
+set(SYSROOT_DIR   ${ZEPHYR_SDK_INSTALL_DIR}/${SYSROOT_TARGET}/${SYSROOT_TARGET})
+set(CROSS_COMPILE ${ZEPHYR_SDK_INSTALL_DIR}/${CROSS_COMPILE_TARGET}/bin/${CROSS_COMPILE_TARGET}-)
 
 if("${ARCH}" STREQUAL "x86")
   if(CONFIG_X86_64)