split up functions/scripts a bit. downloads avr-gcc

cmake/AddKeyboard.cmake

@@ -0,0 +1,46 @@
+macro(add_keyboard KEYBOARD_CMAKE)
+  get_filename_component(KEYBOARD_FULL_DIRECTORY "${KEYBOARD_CMAKE}" DIRECTORY)
+
+  # find the right toolchain
+  file(READ ${KEYBOARD_FULL_DIRECTORY}/info.json JSON_STRING)
+  string(JSON PROCESSOR GET ${JSON_STRING} processor)
+  if(${PROCESSOR} MATCHES "^at.*")
+    set(PLATFORM "avr")
+    # find_package(avr-gcc)
+  elseif(
+    ${PROCESSOR} MATCHES "^STM.*" OR
+    ${PROCESSOR} MATCHES "^WB32.*" OR
+    ${PROCESSOR} MATCHES "^MK.*" OR
+    ${PROCESSOR} MATCHES "RP2040" OR
+    ${PROCESSOR} MATCHES "^GD32.*")
+    set(PLATFORM "chibios")
+  endif()
+  if(NOT DEFINED PLATFORM)
+    message(FATAL_ERROR "Could not find platform for ${KEYBOARD_FULL_DIRECTORY}")
+  endif()
+
+  include(FindToolChain)
+  find_toolchain()
+
+  file(RELATIVE_PATH KEYBOARD_FOLDER "${CMAKE_SOURCE_DIR}/keyboards" "${KEYBOARD_FULL_DIRECTORY}")
+  string(REPLACE "/" "." KEYBOARD_NAME ${KEYBOARD_FOLDER})
+  ExternalProject_Add(${KEYBOARD_NAME}
+    SOURCE_DIR ${CMAKE_SOURCE_DIR}
+    PREFIX ${CMAKE_SOURCE_DIR}/build/keyboards/${KEYBOARD_FOLDER}
+    TMP_DIR ${CMAKE_SOURCE_DIR}/build/keyboards/${KEYBOARD_FOLDER}/tmp
+    DOWNLOAD_DIR ${CMAKE_SOURCE_DIR}/build/keyboards/${KEYBOARD_FOLDER}/Download
+    BINARY_DIR ${CMAKE_SOURCE_DIR}/build/keyboards/${KEYBOARD_FOLDER}/Build
+    STAMP_DIR ${CMAKE_SOURCE_DIR}/build/keyboards/${KEYBOARD_FOLDER}/Stamp
+    LOG_DIR ${CMAKE_SOURCE_DIR}/build/keyboards/${KEYBOARD_FOLDER}/Log
+    INSTALL_DIR ${CMAKE_SOURCE_DIR}/build/keyboards/${KEYBOARD_FOLDER}/Install
+    INSTALL_COMMAND cmake -E echo "No install needed"
+    # this seems to work well for all systems so far - not sure if it'd be useful to customize
+    CMAKE_GENERATOR "Unix Makefiles"
+    CMAKE_ARGS 
+      -DCMAKE_TOOLCHAIN_FILE=${CMAKE_SOURCE_DIR}/platforms/${PLATFORM}/toolchain.cmake
+      -DTOOLCHAIN_ROOT=${TOOLCHAIN_ROOT}
+      -DMAKE_ROOT=${MAKE_ROOT}
+      -DQMK_KEYBOARD=${KEYBOARD_NAME}
+      -DQMK_KEYBOARD_FOLDER=${KEYBOARD_FOLDER}
+  )
+endmacro(add_keyboard)