Hello,
first of all, thank you for reporting this issue!
We were able to reproduce the problem, which can happen in all STM32 Build Environments (Version 11.00) when they are installed at a location with a short path (e.g. C:\STM32).
The GCC ARM embedded toolchain (Version 10-2020-q4-major) is then creating dependency files with erroneous path entries (e.g. C\:\STM32). As a result the next 'make' fails with 'no rule to make target C\:\STM32\...' (note the additional \ after the drive letter).
We have now updated all STM32 Build Environments to Version 11.00.01 which contain a downgrade of GCC ARM embedded toolchain from 10-2020-q4-major back to 9-2020-q2-update used for building the binary.
You can register once more and download the new version.
Thanks and best regards,
Manfred.