Override of "add_psp_module" for coverage test gets global scope

[jphickey]

Describe the bug
In order to (attempt to) implement coverage test for PSP modules without redefining the sources for that module, the Cmake script currently redefines the add_psp_module function to do something different when building for coverage tests.

Problem is, this override ends up getting global scope, not directory scope. So in the event that multiple modules are specified and if the psp library gets built first (which will include coverage test if enabled), then any modules built after the psp will fail, because they use the coverage test override function rather than the proper function as defined in arch_build.cmake

To Reproduce
Create a project utilizing several PSP modules/extensions for custom HW access. Modules will fail to build when ENABLE_UNIT_TESTS is set true, even if they do not contain a coverage test, because the FSW build is using the wrong definition of the add_psp_module function.

Expected behavior
Should build successfully.

Code snips
Root of the problem is this override at:

PSP/unit-test-coverage/modules/CMakeLists.txt

Line 14 in 6d40816

function(add_psp_module MODULE_NAME)

System observed on:
Ubuntu

Additional context
This function definition ends up getting global scope, not directory scope, so even after returning to the parent directory, this modified definition remains active.

Reporter Info
Joseph Hickey, Vantage Systems, Inc.