Enable PIC to ucd CMakeLists

https://github.com/espeak-ng/espeak-ng/issues/1972

src/ucd-tools/CMakeLists.txt

@@ -6,4 +6,7 @@ add_library(ucd STATIC
   src/scripts.c
   src/tostring.c
 )
+# enable PIC in order to embed libucd.a in a .so
+set_property(TARGET ucd PROPERTY POSITION_INDEPENDENT_CODE ON)
+
 target_include_directories(ucd PUBLIC src/include)