cmake: Detecting C compile features - failed

Hi,

When I try to use qrintf with cmake, I got following errors:

```bash
➜ cmake-build-debug git:(master) CC="/usr/local/bin/qrintf cc" cmake ..
-- The C compiler identification is GNU 8.1.0
-- Check for working C compiler: /usr/local/bin/qrintf
-- Check for working C compiler: /usr/local/bin/qrintf -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - failed
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Looking for pthread_create
-- Looking for pthread_create - not found
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE
-- Configuring done
-- Generating done

```

As you can see, the cmake try to test the C compile features, but it failed.

How we integrate qrintf with cmake?

Reproduce the reported command with CC="/usr/local/bin/qrintf cc" cmake .. and inspect the CMake configure output around "Detecting C compile features". Trace how qrintf handles CMake's compiler probes and determine what successful integration should report; done means configuration completes without the compile-features failure.

Written by the indexing model from the issue text.