[ns] Linking a C stack

I'm trying to link an existing protocol stack into NS3, the only problem
is that it's written in C, and I've never used waf before, so I've no
idea what the best way of specifying a C file is.

I tried just
adding it to the modules.source definition in the appropriate wscript
file, and while it now compiles, I'm getting a link error for malloc:

/usr/bin/ld:
src/mystack/model/mystack.c.1.o: relocation R_X86_64_PC32 against
undefined symbol `malloc@@GLIBC_2.2.5' can not be used when making a
shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value

If anyone has any pointers, it would be greatly appreciated!

Mike.