Remove mem_manager.o from libmain.a (#1630)

cores/esp8266/heap.c

@@ -37,6 +37,11 @@ size_t ICACHE_RAM_ATTR xPortGetFreeHeapSize(void)
     return umm_free_heap_size();
 }
 
+size_t ICACHE_RAM_ATTR xPortWantedSizeAlign(size_t size)
+{
+    return (size + 3) & ~((size_t) 3);
+}
+
 void system_show_malloc(void)
 {
     umm_info(NULL, 1);

tools/sdk/lib/README.md

@@ -3,11 +3,8 @@
 After updating SDK libraries to a new version, do the following changes.
 
 
-1. Weaken symbols from mem_manager.o to use custom heap implementation
+1. Remove mem_manager.o from libmain.a to use custom heap implementation
 
     ```bash
-    xtensa-lx106-elf-ar -x libmain.a mem_manager.o
-    xtensa-lx106-elf-objcopy --weaken mem_manager.o
-    xtensa-lx106-elf-ar -r libmain.a mem_manager.o
-    rm mem_manager.o
+    xtensa-lx106-elf-ar -d libmain.a mem_manager.o
     ```