[BUG] cmake fails to detect RTL_AIRBAND_VERION when using source from a release artifact

[charlie-foxtrot]

As of #450 cmake has an expectation that it is running in a git repo, however when downloading source from a release there is no .git folder

steps to reproduce:

$ wget https://github.com/charlie-foxtrot/RTLSDR-Airband/archive/refs/tags/v5.0.5.tar.gz
$ tar xzf v5.0.5.tar.gz
$ cd RTLSDR-Airband-5.0.5/
$ mkdir build
$ cd build/
$ cmake ../
-- The CXX compiler identification is GNU 11.4.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Error at CMakeLists.txt:13 (message):
  Failed to detect RTL_AIRBAND_VERSION - "fatal: not a git repository (or any
  of the parent directories): .git"


-- Configuring incomplete, errors occurred!
See also "/root/RTLSDR-Airband-5.0.5/build/CMakeFiles/CMakeOutput.log".

[charlie-foxtrot]

Resolved in v5.0.6 by #456