php scenarios do not build with --enable-debug configuration

The php scenarios don't compile with --enable-debug 
```
docker@e3c09a8785b8:/experiment/src$  make
Generating phar.phar

Fatal error: Unknown: Failed opening required 'ext/phar/phar.php' (include_path='.:/usr/local/lib/php') in Unknown on line 0
Makefile:312: recipe for target 'ext/phar/phar.phar' failed
make: *** [ext/phar/phar.phar] Error 255
docker@e3c09a8785b8:/experiment/src$ 
```
