build(PythonPackages): Enable CMAKE_POSITION_INDEPENDENT_CODE

For:

/opt/rh/devtoolset-10/root/usr/libexec/gcc/x86_64-redhat-linux/10/ld: _deps/libcbor-build/src/libcbor.a(serialization.c.o): relocation R_X86_64_32S against `.rodata' can not be used when making a shared object; recompile with -fPIC
2701
/opt/rh/devtoolset-10/root/usr/libexec/gcc/x86_64-redhat-linux/10/ld: _deps/libcbor-build/src/libcbor.a(common.c.o): relocation R_X86_64_32S against `.rodata' can not be used when making a shared object; recompile with -fPIC
2702
collect2: error: ld returned 1 exit status

CMakeLists.txt

@@ -31,6 +31,9 @@ set(_itk_build_testing ${BUILD_TESTING})
 set(BUILD_TESTING OFF)
 set(_itk_build_shared ${BUILD_SHARED_LIBS})
 set(BUILD_SHARED_LIBS OFF)
+if(NOT DEFINED CMAKE_POSITION_INDEPENDENT_CODE)
+  set(CMAKE_POSITION_INDEPENDENT_CODE ON)
+endif()
 
 # Uses newer CMake
 set(RapidJSON_GIT_REPOSITORY "https://github.com/thewtex/rapidjson.git")