Improve functionality to enable mlocati/docker-php-extension-installer to use PIE

[asgrim]

Add PIE support to https://github.com/mlocati/docker-php-extension-installer

See: mlocati/docker-php-extension-installer#1125

Discussed with mlocati on this, some key things would be needed for this to work

• #435 - prompt to (or auto) install missing system dependencies
• #434 - prompt to (or auto) install build tools (gcc/phpize/etc)
• #432 - executable static build of PIE
• #466 - ability to install multiple extensions at once