Allow not forcibly setting CMAKE_C_FLAGS and CMAKE_CXX_FLAGS

[anderslanglands]

I hit the same issue as #133

The reason is that even if no cflags or cxxflags are specified in the Config, it will still forcibly set those in the cfg, even if no_default_flags is forced to true (in that case CMAKE_C(XX)_FLAGS is just set to empty).

This causes some libraries to fail to build on windows because of the missing /EHsc flag that CMake sets by default, but is apparently not in the list that Config pulls from cc.

I would expect that if I don't supply any flags to Config, then I should get the exact same result as calling cmake in the terminal, which is not what happens currently. Is there a way we can change this behaviour?

[Zagitta]

I'm facing this exact issue here as well: alianse777/darknet-rust#10

There really needs to be a way to instruct cmake-rs to not set those flags

[Blonteractor]

I am facing the same issue, the build command works when CMAKE_C_FLAGS and CMAKE_CXX_FLAGS are not passed in, but this lib always passes them as something and even when they are empty it doesnt work.

[Chiichen]

The same on me LibVNC/libvncserver#628! I'm not an expert on cmake. I can not find out the reson that these builds failed on. I think adding a flag like force_no_default_flags to pass no_default_setting=true to crate cc works. I will give it a try

[Chiichen]

I've opend a PR(#219 ) for this. You can try this in https://github.com/Chiichen/cmake-rs/tree/feat-force-no-default-flags