cmake: fallback if both openexr build types are not available

cmake/FindOpenEXR.cmake

@@ -130,9 +130,18 @@ foreach (COMPONENT ${_openexr_components})
                   HINTS ${OPENEXR_LIBRARY_DIR} $ENV{OPENEXR_LIBRARY_DIR}
                         ${GENERIC_LIBRARY_PATHS} )
 
+    if (OPENEXR_${UPPERCOMPONENT}_LIBRARY_RELEASE AND OPENEXR_${UPPERCOMPONENT}_LIBRARY_DEBUG)
       set(OPENEXR_${UPPERCOMPONENT}_LIBRARY
         optimized ${OPENEXR_${UPPERCOMPONENT}_LIBRARY_RELEASE}
         debug ${OPENEXR_${UPPERCOMPONENT}_LIBRARY_DEBUG})
+    elseif(OPENEXR_${UPPERCOMPONENT}_LIBRARY_RELEASE)
+      set(OPENEXR_${UPPERCOMPONENT}_LIBRARY
+        ${OPENEXR_${UPPERCOMPONENT}_LIBRARY_RELEASE})
+    else()
+      set(OPENEXR_${UPPERCOMPONENT}_LIBRARY
+        ${OPENEXR_${UPPERCOMPONENT}_LIBRARY_DEBUG})
+    endif()
+
 endforeach ()
 
 find_package_handle_standard_args (OpenEXR