project-config.jam missing path to python interpreter (boost 1.78.0)

project-config.jam generated is missing the path to the interpreter, and therefore b2 will fail to build the python3 libraries.

Simplified example below.

Running:
```
./bootstrap.sh --with-python=/Library/Frameworks/Python.framework/Versions/3.10/bin/python3
```

will generate the line:
```
using python : 3.10 : "/Library/Frameworks/Python.framework/Versions/3.10" ;
```

which will fail when building, because it is invoking "python" instead of "python3" even if it was specified in in the bootstrap command:
```
notice: [python-cfg] Checking interpreter command "/Library/Frameworks/Python.framework/Versions/3.10/bin/python"...
notice: [python-cfg] running command '/Library/Frameworks/Python.framework/Versions/3.10/bin/python -c "from sys import *; print('version=%d.%d\nplatform=%s\nprefix=%s\nexec_prefix=%s\nexecutable=%s' % (version_info[0],version_info[1],platform,prefix,exec_prefix,executable))" 2>&1'
notice: [python-cfg] ...does not invoke a working interpreter
```