Include stub hash in generated arginfo files

[nikic]

The hash is used to check whether the arginfo file needs to be regenerated. PHP-Parser will only be downloaded if this is actually necessary.

This ensures that release artifacts will never try to regenerate stubs and thus fetch PHP-Parser, as long as you do not modify any files.

[nikic]

@remicollet This is the idea I mentioned yesterday, to ensure that there is no attempt to regenerate stubs if they haven't changed.

[nikic]

A disadvantage of this change is that stub changes will be prone to merge conflicts.

[cmb69]

Hmm, that's bad, but AIUI it's a normal SHA1 of the stub file, so could be worked around. Not sure.

[remicollet]

Looks like this change is really needed....

For this morning, trying to build alpha1

+ make -C build-embedded install-sapi install-headers INSTALL_ROOT=/builddir/build/BUILDROOT/php80-php-8.0.0~alpha1-20.fc31.remi.x86_64
make: Entering directory '/builddir/build/BUILD/php-8.0.0alpha1/build-embedded'
Parse /builddir/build/BUILD/php-8.0.0alpha1/ext/spl/spl_directory.stub.php to generate /builddir/build/BUILD/php-8.0.0alpha1/ext/spl/spl_directory_arginfo.h
sh: wget: command not found
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
^M  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0curl: (6) Could not resolve host: github.com
Failed to download PHP-Parser tarball

Workaround used for now

for i in $(find ext sapi Zend -name \*stub.php); do
  touch -c -r $i ${i/.stub.php/_arginfo.h}
done