[TF-M] Following the TF-M build example

I'm following the first build example in docs\getting_started\tfm_build_instruction.rst, for the mps2/an521. cmake -S . -B cmake_build -DTFM_PLATFORM=mps2/an521 -DCMAKE_TOOLCHAIN_FILE=toolchain_GNUARM.cmake

Building on Windows with gnu, it progresses pretty far then stops with the error shown below.

Any suggestions? Kevin

-- Configuring done CMake Error at toolchain_GNUARM.cmake:114 (add_library): No SOURCES given to target: tfm_s_scatter Call Stack (most recent call first): platform/ext/target/mps2/an521/CMakeLists.txt:27 (target_add_scatter_file)

CMake Error at toolchain_GNUARM.cmake:114 (add_library): No SOURCES given to target: tfm_ns_scatter Call Stack (most recent call first): platform/ext/target/mps2/an521/CMakeLists.txt:40 (target_add_scatter_file)

CMake Error at toolchain_GNUARM.cmake:114 (add_library): No SOURCES given to target: bl2_scatter Call Stack (most recent call first): platform/ext/target/mps2/an521/CMakeLists.txt:63 (target_add_scatter_file)

CMake Generate step failed. Build files cannot be regenerated correctly.