Shared Library

[bmhan12]

This PR:

• Sets the default to build geosx_core as a shared library
  • For clang@upstream on lassen release, build directory size from static to shared: 13GB --> 4.4 GB
  • For [email protected] on quartz release, build directory size from static to shared: 4.2GB --> 1.5 GB
• Add CMake config output for what CMake targets are being built and linking behavior for each configuration of GEOSX_BUILD_SHARED_LIBS and GEOSX_BUILD_OBJ_LIBS
• Related to #2023

As part of this PR I also tried building geosx_core as a static library and linking executables to geosx_core, but ran into the errors detailed in issue #2016 . This is likely related to circular dependencies exposed by building GEOSX this way.

[bmhan12]

Moving this out of the merge queue... seeing the lassen integrated tests hang with shared libraries (or might be my terminal/ allocation). Need to debug further against develop.

[rrsettgast]

Moving this out of the merge queue... seeing the lassen integrated tests hang with shared libraries (or might be my terminal/ allocation). Need to debug further against develop.

Maybe ask LC for help

[rrsettgast]

@bmhan12 what happens if you use cmake object libraries, statically link geosx, and dynamically link all unit tests?

[bmhan12]

For future note: Discussed with @white238 about object libraries going forward - We do not want to be using object libraries (additional discussion here - cmake actually does not officially support separable compilation for object libraries).

I have set the default settings to building geosx_core as a shared library, and each component library as a static library. This will use blt_combine_static_library to resolve circular dependency issues.