g++ compile error: `.rodata' can not be used when making a shared object; recompile with -fPIC

As it seems gcc is trying to produce a position-independent executable ("shared object" is the hint), tell it not to:

g++ --std=c++11 -no-pie -Iincludes parser.cpp lib/main-parser.o lib/lib.a

It seems that g++ produces position-independent executables by default on your system. Other systems would require -pie to do so. Using -no-pie should create a "regular" (position dependent) executable.

/usr/bin/ld: lib/lib.a(csdocument.o): relocation R_X86_64_32 against '.rodata' \
can not be used when making a shared object; recompile with -fPIC

This linker error is telling you that the object file csdocument.o in the static library lib/lib.a is not Position Independent Code and hence cannot be linked with your PIE program. So you need to recompile the source files of lib/lib.a with -fPIC, then rebuild the static library, then link it with your PIE program. If you don't have control of the libary sources then request a PIC build from its supplier.

(Others have questioned why you should need to build a PIE target at all since it's not a shared library. In Debian 9, GCC produces PIE executables by default, whether programs or shared libraries. The same goes for Ubuntu as of 17.04. )