The -mcpu=cortex-a9 flag conflicts with the march=armv7-a flag.
Opted to keep mcpu=cortex-a9 as it is more specific and
allows GCC to perform better optimization.

The compiler is also changed to use soft-float ABI as it
was necessary to successfully build. Without it the application
appears to be built with soft-float ABI and it conflicts with
the previous setting which was built with hard-float ABI.
This may be related to: https://gitlab.kitware.com/cmake/cmake/-/issues/21173