CMake: Add install target

Do **not** use this with /usr or /usr/local. It creates subdirectories
for resources/translations in the install prefix.

It's intended for creating a relocatable, self-contained bundle, which
can be packaged.

CMakeModules/DuckStationUtils.cmake

@@ -221,3 +221,9 @@ function(get_scm_version)
     set(SCM_VERSION ${LOCAL_SCM_VERSION} PARENT_SCOPE)
   endif()
 endfunction()
+
+function(install_imported_dep_library name)
+  get_target_property(SONAME "${name}" IMPORTED_SONAME_RELEASE)
+  get_target_property(LOCATION "${name}" IMPORTED_LOCATION_RELEASE)
+  install(FILES "${LOCATION}" RENAME "${SONAME}" DESTINATION "${CMAKE_INSTALL_PREFIX}")
+endfunction()