Always use -fPIC when compiling on Linux
Always use -fPIC when compiling on Linux

to fix the following linker error on Ubuntu 17.04:
> relocation R_X86_64_32 against `.rodata.str1.16' can not be used when making a shared object

emlai/delta,emlai/delta,delta-lang/delta,delta-lang/delta,emlai/delta,emlai/delta,delta-lang/delta,delta-lang/delta