Installing from Source
You should only be building fldigi locally if the binary distribution
does not work on your Linux distribution. Unless you are
modifying the code or need to compile for debugging you will not have
any additional functionality over the binary files. The source
code for fldigi is very large and has a number of dependencies that
must be satisfied before a successful compile. If you are not
familiar with compiling and linking source code you should probably
practice on a simpler package before treading these waters.
Please refer to the following web site for information on building for Linux, Windows and OS X.
Fldigi WIKI - build instructions