Build: Use PIC for jsimd_none.o in shared libs In theory, all objects that will be included in a Un*x shared library must be built using PIC. In practice, most compilers don't require PIC to be explicitly specified for jsimd_none.o, either because the compiler automatically enables PIC in all cases (Ubuntu) or because the size of the generated object is too small. But some rare compilers do require PIC to be explicitly specified for jsimd_none.o. Fixes #520