Avoid using aux_source_directory

[jphickey]

Is your feature request related to a problem? Please describe.
The example build script should not use aux_source_directory() as it is not well defined/controlled behavior - it depends on files that existed at the time "prep" was run.

Describe the solution you'd like
CMakeLists.txt should list the app source files explicitly. This is recommended CMake practice for most normal build cases.

Additional context
This is a prime example of why aux_source_directory() is discouraged, because in this case it incorrectly pulled in the "sample_table.c" source file into the app binary. This is incorrect; the table file is built separately by the table generator script.

Requester Info
Joseph Hickey, Vantage Systems, Inc.