cmake build: CACHE OUT-OF-DATE Syndrome with addFSeamTests()

[jenisys]

Describe the bug
addFSeamTests() macro-call and the generate cmake-snippet to build the generated MockClass sources seem to get out-of-sync sometimes. For example, if you remove an item from the TO_MOCK parameter-list (after a build), its generated sources seem to be used during the next build.

To Reproduce

1. Build "FSeam_tutorial" with cmake (and run tests; all should pass)
2. Remove an item from the TO_MOCK parameter-list in a addFSeamTests() macro-call
3. Build with cmake again (succeeds but should-fail because MockedClass parts should be missing now)

Expected behavior
cmake builds:

• The addFSeamTests() macro-call in a "CMakeLists.txt" and the generated sources/cmake-snippet should stay in sync.
• clean-target: Generated source files and cmake-snippet should be removed when using the clean target of the build system. This simplifies to reach a stable state again (without need to remove the complete cmake build-dir)