Do not override LHCb compilation flags
Geant4 default configuration overrides compiler flags between the load of CMAKE_TOOLCHAIN_FILE
and the test compilations CMake runs to validate the compiler.
This is not a major issue with gcc (apart from using options we do not expect), but it causes the configuration failure of clang because it overrides the mandatory option --gcc-toolchain=...
that we set in the CMAKE_TOOLCHAIN_FILE
.
This MR prevents Geant4 to overrides our settings.
Closes #3 (closed)