add mdk4 and iar upport

bsp/gd32450z-eval/gd32_rom.icf

+/*###ICF### Section handled by ICF editor, don't touch! ****/
+/*-Editor annotation file-*/
+/* IcfEditorFile="$TOOLKIT_DIR$\config\ide\IcfEditor\cortex_v1_0.xml" */
+/*-Specials-*/
+define symbol __ICFEDIT_intvec_start__ = 0x08000000;
+/*-Memory Regions-*/
+define symbol __ICFEDIT_region_ROM_start__ = 0x08000000;
+define symbol __ICFEDIT_region_ROM_end__   = 0x082FFFFF;
+define symbol __ICFEDIT_region_RAM_start__ = 0x20000000;
+define symbol __ICFEDIT_region_RAM_end__   = 0x2002FFFF;
+/*-Sizes-*/
+define symbol __ICFEDIT_size_cstack__ = 0x2000;
+define symbol __ICFEDIT_size_heap__   = 0x2000;
+/**** End of ICF editor section. ###ICF###*/
+
+export symbol __ICFEDIT_region_RAM_end__;
+
+define symbol __region_RAM1_start__ = 0x10000000;
+define symbol __region_RAM1_end__   = 0x1000FFFF;
+
+define memory mem with size = 4G;
+define region ROM_region   = mem:[from __ICFEDIT_region_ROM_start__   to __ICFEDIT_region_ROM_end__];
+define region RAM_region   = mem:[from __ICFEDIT_region_RAM_start__   to __ICFEDIT_region_RAM_end__];
+define region RAM1_region  = mem:[from __region_RAM1_start__   to __region_RAM1_end__];
+
+define block CSTACK    with alignment = 8, size = __ICFEDIT_size_cstack__   { };
+define block HEAP      with alignment = 8, size = __ICFEDIT_size_heap__     { };
+
+initialize by copy { readwrite };
+do not initialize  { section .noinit };
+
+place at address mem:__ICFEDIT_intvec_start__ { readonly section .intvec };
+
+place in ROM_region   { readonly };
+place in RAM_region   { readwrite,
+                        block CSTACK, block HEAP };                        
+place in RAM1_region  { section .sram };
\ No newline at end of file