fatfs_mkimage application fails to build on Ubuntu 16

[keithm-xmos]

System Info Ubuntu 16 CMake v3.24 GCC version unknown

This PR did not fix the issue: https://github.com/xmos/fwk_rtos/commit/3ba2943a45ba5bc5e4d656ce877f887ba02d7b82

Need to be able to reproduce in order to verify a fix.

[keithm-xmos]

Perhaps we need to use target_link_libraries(m etc...)

See: https://stackoverflow.com/questions/34625627/how-to-link-to-the-c-math-library-with-cmake

[mbanth]

This issue is now tracked in Jira AP-136.