Define cmake target as PIC if BUILD_SHARED_LIBS

[langchr86]

What language does this apply to?
Generated C/C++ code and the specific cmake target.

Describe the problem you are trying to solve.
When I link to the generated cmake target and set the BUILD_SHARED_LIBS variable globally I get linker errors because the protobuf created code is not relocateable.

Describe the solution you'd like
In my user code I use something like the following:

# ensure relocateable code
if (BUILD_SHARED_LIBS)
  set_property(TARGET ${PROTO_TARGET} PROPERTY POSITION_INDEPENDENT_CODE TRUE)
endif ()

But this could be integrated in the cmake part of this project directly.

Describe alternatives you've considered
It's not a big problem. But may be helpful for people that do not have that much cmake experience.

Additional context
Nothing.

[enum-class]

I do not think the problem is about POSITION_INDEPENDENT_CODE , because already the code in CMakeLists.txt in line 109 set CMAKE_POSITION_INDEPENDENT_CODE property on

[langchr86]

But this line is only relevant if the whole project is loaded as sub-project with add_subdirectory and built as part of the whole project. In my case I load the cmake modules from the already compiled and installed library to only use protoc with protobuf_generate and include the generated source files in my own project.