Remove sed from ld_script, replace with INCLUDEs

ld_script.txt

@@ -13,7 +13,7 @@ SECTIONS {
 
         . = 0x1C000;
 
-<EWRAM>
+        INCLUDE "sym_ewram.ld"
 
         . = 0x40000;
 }
@@ -24,13 +24,13 @@ SECTIONS {
     ALIGN(4)
     {
         /* .bss starts at 0x3000000 */
-<BSS>
+        INCLUDE "sym_bss.ld"
 
         /* .bss.code starts at 0x3001AA8 */
         src/m4a_2.o(.bss.code);
 
         /* COMMON starts at 0x30022A8 */
-<COMMON>
+        INCLUDE "sym_common.ld"
         *libc.a:sbrkr.o(COMMON);
         end = .;
         . = 0x8000;