find libraries by name instead of using the imported location

Instead of directly using an imported location we use
the soname if possible and after that the location name
to find the library using the location directory as hint.

This allows us to use an soname, which may be different
and to the location name (and residing directory). This
allows to use system installed libraries which may be updated
but are compatible with the one used at built time
as long as the location and name in which they were found in
are the same.

cmake/catkin_libraries.cmake

@@ -114,6 +114,40 @@ function(catkin_unpack_libraries_with_build_configuration VAR)
   set(${VAR} "${result}" PARENT_SCOPE)
 endfunction()
 
+#
+# Find libraries by imported location or soname with location dir as hint
+#
+# :param VAR: the output variable name
+# :type VAR: string
+# :param LIB: the imported target to find the library for
+# :type LIB: string
+# :type ARGN: selected config to query in the target's properties
+# :type ARGN: string
+#
+# @public
+#
+function(catkin_find_library_imported_location_library VAR LIB)
+  set(lib ${LIB})
+  if(ARGN)
+    set(cfg _${ARGN})
+  endif()
+  set(imported_location_libnames)
+  get_target_property(imported_soname ${lib} IMPORTED_SONAME${cfg})
+  if(imported_soname)
+    list(APPEND imported_location_libnames ${imported_soname})
+  endif()
+  get_target_property(imported_location ${lib} IMPORTED_LOCATION${cfg})
+  if(imported_location)
+    get_filename_component(imported_location_name ${imported_location} NAME)
+    get_filename_component(imported_location_dir ${imported_location} DIRECTORY)
+    list(APPEND imported_location_libnames ${imported_location_name})
+  endif()
+  if(imported_location_libnames)
+    find_library(imported_location_library NAMES ${imported_location_libnames} HINTS ${imported_location_dir})
+  endif()
+  set(${VAR} "${imported_location_library}" PARENT_SCOPE)
+endfunction()
+
 #
 # Replace imported library target names with the library name.
 #
@@ -142,10 +176,9 @@ function(catkin_replace_imported_library_targets VAR)
           list(APPEND result ${${lib}_resolved_libs})
         endif()
       elseif(${${lib}_imported})
-        set(imported_libraries)  # empty list
-        get_target_property(${lib}_imported_location ${lib} IMPORTED_LOCATION)
-        if(${lib}_imported_location)
-          list(APPEND imported_libraries ${${lib}_imported_location})
+        catkin_find_library_imported_location_library(${lib}_imported_location_library ${lib})
+        if(${lib}_imported_location_library)
+          list(APPEND imported_libraries ${${lib}_imported_location_library})
         else()
           get_target_property(${lib}_imported_configurations ${lib} IMPORTED_CONFIGURATIONS)
           foreach(cfg ${${lib}_imported_configurations})
@@ -156,11 +189,14 @@ function(catkin_replace_imported_library_targets VAR)
               if(NOT ${lib}_imported_location_${cfg})
                 get_target_property(${lib}_imported_location_${cfg} ${lib} IMPORTED_LOCATION_${cfg})
               endif()
+              if(${lib}_imported_location_${cfg})
+                list(APPEND imported_libraries ${${lib}_imported_location_${cfg}})
+              endif()
             else()
-              get_target_property(${lib}_imported_location_${cfg} ${lib} IMPORTED_LOCATION_${cfg})
-            endif()
-            if(${lib}_imported_location_${cfg})
-              list(APPEND imported_libraries ${${lib}_imported_location_${cfg}})
+              catkin_find_library_imported_location_library(${lib}_imported_location_library_${cfg} ${lib} ${cfg})
+              if(${lib}_imported_location_library_${cfg})
+                list(APPEND imported_libraries ${${lib}_imported_location_library_${cfg}})
+              endif()
             endif()
           endforeach()
         endif()