Hello Francois Poucheret,
SDK_2.2_LPCXpresso54608 folder already have the armgcc toolchain, the folder is:
SDK_2.2_LPCXpresso54608\tools\cmake_toolchain_files

Wish it helps you!
Have a great day,
Kerry
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------