cmake: locating zephyr modules in CMAKE_BINARY_DIR

This commit restores the old behaviour of locating Zephyr modules under
CMAKE_BINARY_DIR instead of CMAKE_CURRENT_BINARY_DIR during building of
Zephyr modules.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5f13617..2942954 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -480,7 +480,7 @@
     # https://cmake.org/pipermail/cmake/2019-June/069547.html
     string(TOUPPER ${module_name} MODULE_NAME_UPPER)
     set(ZEPHYR_CURRENT_MODULE_DIR ${ZEPHYR_${MODULE_NAME_UPPER}_MODULE_DIR})
-    add_subdirectory(${ZEPHYR_CURRENT_MODULE_DIR} ${CMAKE_CURRENT_BINARY_DIR}/modules/${module_name})
+    add_subdirectory(${ZEPHYR_CURRENT_MODULE_DIR} ${CMAKE_BINARY_DIR}/modules/${module_name})
   endforeach()
   # Done processing modules, clear ZEPHYR_CURRENT_MODULE_DIR.
   set(ZEPHYR_CURRENT_MODULE_DIR)