x11-fm/doublecmd: fix build

After recent changes to lang/fpc port, x11-fm/doublecmd is failing to build.
FpPipe() function now requires 2 parameters instead of one.

The attached patch fixes it.

PR: 244655
Submitted by: Beñat Gonzalez Etxepare <bbtruk@users.sourceforge.net> (maintainer)