Enable building of libyosys.so

[macd]

Yosys has the ability to build Python wrappers for a large part of the RTLIL and it produces a libyosys.so when ENABLE_PYOSYS := 1 However, with UHDM this doesn't work because it is making a static library. Is there a way to also build a .so so that a libyosys.so can be built? Here is the relevant error msg:

[100%] Building yosys
[100%] Building libyosys.so
/usr/bin/ld: ./../image/lib/uhdm/libkj.a(exception.c++.o): relocation R_X86_64_TPOFF32 against `_ZN2kj12_GLOBAL__N_1L19threadLocalCallbackE' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: ./../image/lib/uhdm/libuhdm.a(clone_tree.cpp.o): relocation R_X86_64_PC32 against symbol `_ZTVN4UHDM9attributeE' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: bad value
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[1]: *** [Makefile:678: libyosys.so] Error 1
make[1]: *** Waiting for unfinished jobs....
make[1]: Leaving directory '/home/macd/oroad/code/uhdm-integration/yosys'
make: *** [Makefile:32: yosys/yosys] Error 2