Well, partially I've managed to solve the problem of building Lazarus. I've added an PPC_EXEC_PATH parameter.
make clean all FPC=/home/guest/fpc/bin/fpc PPC_EXEC_PATH=/home/guest/fpc/bin/
The problem is that each and every time I try to compile a Lazarus project, even the default empty form, I get a message like: project1.lpr(24,1) Error: Resource compiler "fpcres" not found, switching to external mode. It's the same error.
How do I force Lazarus to use this PPC_EXEC_PATH parameter when compiling any project, including rebuilding Lazarus using the entry in the "Tools" menu?