[cmake/FindGEOS] Add FindPackageHandleStandardArgs fallback if GEOS n…

…ot found (#1977)

This should make the module slightly more user-friendly by correctly
handling explicit specification of GEOS_INCLUDE_DIR and GEOS_LIBRARY.

cmake/modules/FindGEOS.cmake

@@ -162,6 +162,19 @@ IF (GEOS_INCLUDE_DIR AND GEOS_LIBRARY)
    SET(GEOS_FOUND TRUE)
 ENDIF (GEOS_INCLUDE_DIR AND GEOS_LIBRARY)
 
+if (NOT GEOS_INCLUDE_DIR OR NOT GEOS_LIBRARY)
+  include(SelectLibraryConfigurations)
+  select_library_configurations(GEOS)
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(GEOS REQUIRED_VARS GEOS_LIBRARY GEOS_INCLUDE_DIR)
+  if(GEOS_FOUND)
+    set(GEOS_INCLUDE_DIRS ${GEOS_INCLUDE_DIR})
+    if(NOT GEOS_LIBRARIES)
+      set(GEOS_LIBRARIES ${GEOS_LIBRARY})
+    endif()
+  endif()
+endif()
+
 IF (GEOS_FOUND)
 
    IF (NOT GEOS_FIND_QUIETLY)