[utest][stm32f412][gcc] add __rt_utest_tc_tab_start to support utest

Author: mysterywolf

bsp/stm32/stm32f412-st-nucleo/board/linker_scripts/link.lds

@@ -40,6 +40,12 @@ SECTIONS
         KEEP(*(VSymTab))
         __vsymtab_end = .;
 
+        /* section information for utest */
+        . = ALIGN(4);
+        __rt_utest_tc_tab_start = .;
+        KEEP(*(UtestTcTab))
+        __rt_utest_tc_tab_end = .;
+
         /* section information for initial. */
         . = ALIGN(4);
         __rt_init_start = .;