trying to fix building on esp-idf

CMakeLists.txt

@@ -1,10 +1,16 @@
 cmake_minimum_required(VERSION 3.5)
-project(u8g2)
 
 set(COMPONENT_ADD_INCLUDEDIRS csrc)
 file(GLOB COMPONENT_SRCS csrc/*.c)
 file(GLOB COMPONENT_HDRS csrc/*.h)
 
+if(COMMAND idf_component_register)
+        idf_component_register(SRCS "${COMPONENT_SRCS}" INCLUDE_DIRS csrc)
+        return()
+endif()
+
+project(u8g2)
+
 if(COMMAND register_component)
         set(COMPONENT_NAME ".")
         register_component()