[nrf fromlist] cmake: define ZEPHYR_TOOLCHAIN_PATH

Other toolchains uses <toolchain>_TOOLCHAIN_PATH, align Zephyr SDK
by setting ZEPHYR_TOOLCHAIN_PATH to be identical to the
ZEPHYR_SDK_INSTALL_DIR.

Upstream PR: zephyrproject-rtos/zephyr#79118

Signed-off-by: Torsten Rasmussen <[email protected]>

Author: tejlmand

cmake/modules/FindZephyr-sdk.cmake

@@ -175,3 +175,4 @@ if(LOAD IN_LIST Zephyr-sdk_FIND_COMPONENTS)
     endif()
   endif()
 endif()
+set(ZEPHYR_TOOLCHAIN_PATH ${ZEPHYR_SDK_INSTALL_DIR})