Default compile should work without conan

[aboseley]

It would be nice to be able to compile and run the tests without conan if catch2 is already 'find' able, thru cmake find package.

Also default make,build, install cycle should work, without conan which is only used for test

mkdir build
cd build
cmake .. -DCMAKE_INSTALL_PREFIX=~/somewhere
make -j
make install

[bernedom]

Building & installing without conan should work if the tests are not needed.

@aboseley can you post your cmake error messages?

I will think about trying to find the system package of catch2 first for the tests