If you get this error, it is often because you have configured Apache with modules that weren't actually installed. Eg. you try to load the PHPmodule but didn't actually install the apache2 php module, so the server can't start. In general, this error can often be caused by issues with problematic modules and/or Apache being configured for modules that have not actually be installed (eg. libapache2-mod-php) is missing.
The above results in this less than obv........
The solution is just to install libmicrohttpd-dev
./xmr-stak
./xmr-stak: error while loading shared libraries: libmicrohttpd.so.10: cannot open shared object file: No such file or directory
libmicrohttpd
libmicrohttpd10 - library embedding HTTP server functionality
libmicrohttpd-dbg - library embedding HTTP server functionality (debug)
libmicrohttpd-dev - library embedding HTTP server functionality (development)
$ sudo apt-get i........