Binary with the name "python" required

[s9105947]

When the current environment holds no binary python, the build crashes at compilation time. (See full log below)

Note: Maybe this issue should be moved to the firestarter repo, I don't know if this is still an issue upstream.

This is a problem for the more recent versions of debian, which only have a python3 binary, as the binary python has always referred to version 2.7 in that context.

Workaround: start from python virtual environment

Fix: Detect/Configure the python binary path correctly and incorporate python3

[  3%] Create FIRESTARTER source code directory
[  7%] Generate FIRESTARTER source code
/usr/bin/env: 'python': No such file or directory
make[2]: *** [CMakeFiles/libfirestarter.dir/build.make:136: firestarter/Makefile] Error 127
make[1]: *** [CMakeFiles/Makefile2:314: CMakeFiles/libfirestarter.dir/all] Error 2
make: *** [Makefile:160: all] Error 2

[bmario]

Luckily, the new FIRESTARTER should solve this problem, but please don't use your time on that.