I finally got Bison to work for the first time for LIR Compiler.
The error was in the makefile itself - a statement, though incorrect skipped my notice since it worked for the earlier version using only flex.
What I was doing for making main.o was -
$(CC) $(CFLAGS) $^ -0 $@.
where the dependencies were a .cc file, and a library.
Due to a strange coincidence, this makefile worked fine with my earlier attempts using only flex. With bison also included, things got a little messier, since I had to include the token header tok.h in the dependencies for main.cc. The above line broke down in that case.
The remedy was to replace this line with what should have been there in the first place -
$(CC) $(CFLAGS) -c main.cc -o main.c
and then, include the other libraries in the linking phase when all the .o files were linked.
The makefile and compilation process is starting to make more sense now, although I still don't know what lies inside the .a files.
Once the build is working fine, remains the task of building the parser, which is the fun part. So I should be making good progress with the project in the coming days.