Final images contains a `/usr/src/php.tar.xz` file

[fruit]

Why does images contains a /usr/src/php.tar.xz file (12Mb)?

For example php:7.1-fpm...

[yosifkit]

So that it doesn't have to be downloaded again (and possibly be a slightly different version) for installing extensions.

It was previously kept in extracted form until #256.

[fruit]

Ok, clear.