added some packages required for building

[Fusl]

some of the packages required for building this software, mostly m4, librtlsdr-dev and automake aren't being installed by default if apt has previously been configured not to install suggested and recommended packages as is the case on minimalistic debian installations for example.

[lnxbil]

As seen in #42, we should add pkg-config too.

[Fusl]

thanks for the note, added pkg-config as dependency here too