cmake: Remove the PREBUILT_HOST_TOOLS variable

The PREBUILT_HOST_TOOLS variable was used during the CMake migration
but is no longer documented or needed. As the docs demonstrate, adding
tools to path is an easy way to find prebuilt host tools.

Signed-off-by: Sebastian Boe <[email protected]>

Author: SebastianBoe

cmake/app/boilerplate.cmake

@@ -76,14 +76,6 @@ execute_process(
   OUTPUT_FILE ${ZEPHYR_BINARY_DIR}/include/generated/syscall_macros.h
   )
 
-if(NOT PREBUILT_HOST_TOOLS)
-  set(PREBUILT_HOST_TOOLS $ENV{PREBUILT_HOST_TOOLS})
-  set(PREBUILT_HOST_TOOLS ${PREBUILT_HOST_TOOLS} CACHE PATH "")
-  if("${CMAKE_HOST_SYSTEM_NAME}" STREQUAL "Windows")
-    set(PREBUILT_HOST_TOOLS $ENV{ZEPHYR_BASE}/scripts/prebuilt)
-  endif()
-endif()
-
 if(NOT ZEPHYR_GCC_VARIANT)
   set(ZEPHYR_GCC_VARIANT $ENV{ZEPHYR_GCC_VARIANT})
 endif()

cmake/host-tools.cmake

@@ -1,9 +1,5 @@
 include($ENV{ZEPHYR_BASE}/cmake/host-tools-zephyr.cmake)
 
-if(PREBUILT_HOST_TOOLS)
-  list(APPEND CMAKE_PROGRAM_PATH ${PREBUILT_HOST_TOOLS}/kconfig)
-endif()
-
 # Search for the must-have program dtc on PATH and in
 # TOOLCHAIN_HOME. Usually DTC will be provided by an SDK, but for
 # SDK-less projects like gccarmemb, it is up to the user to install