We don't actually want to do anything with the open()ed file, just
immediately close it.
The CalledProcessError doesn't have its return returncode checked
here, even though other code with the same type of context manager does.
In the case main->subp->subsubp, if subsubp succeed to configure but
subp subsequentially fails, subsubp is still being built but its summary
was missing.
Meson already works like that, except in do_copydir() that requires
absolute destdir. Better explicitly support that instead of leaving it
undefined and unconsistent.
Eli Schwartz
Xavier Claessens
Alois Wohlschlager