The easiest way on Debian would be to use
apt-get install php5-apcu
You might need to add special package repository to
/etc/apt/sources.list, in order to pick this package up:
deb http://packages.dotdeb.org wheezy-php55 all deb-src http://packages.dotdeb.org wheezy-php55 all
I didn't have "make" installed (which is ridiculous, if pecl needs it it should be a dependency and have been installed automatically while installing the above packages)
I second that. It should be a dependency and you should get a proper message during phpize. But i'm unsure, if development tools for building or compiling should be installed automatically.
Possible alternative: use a tool called Pickle.
php pickle.phar install apcu