Only disable `-Wsign-compare` for tests that do not compile cleanly
with this warning enabled. Re-enable the warning for the other tests,
so that it can catch any new occurrences.
Signed-off-by: Sven van Haastregt <sven.vanhaastregt@arm.com>
* Preserve existing release flags in MSVC
Without this the `/MD` flag is lost on Release builds,
resulting in the below error when using a Ninja CMake generator with
VS2019 compiler. Before replacement `/MD /O2 /Ob2 /DNDEBUG`, after replace
`/MD /Od /Ob0 /DNDEBUG`
```
harness.lib(testHarness.cpp.obj) : error LNK2038: mismatch detected for 'RuntimeLibrary': value 'MD_DynamicRelease' doesn't match value 'MT_StaticRelease' in test_conversions.cpp.obj
```
* Remove Visual Studio 2005 release flag workarounds
