gameboy-advance: don't crash copying unaligned strings

Strings are emitted in .rodata sections, which are not yet mentioned in the linker script.

I can't exactly explain why it didn't work before, as these sections should have been included in .bss and thus properly aligned, but it appears to work reliably.

targets/gameboy-advance.ld

@@ -21,6 +21,14 @@ SECTIONS
         . = ALIGN(4);
     } >rom
 
+    .rodata :
+    {
+        . = ALIGN(4);
+        *(.rodata)
+        *(.rodata*)
+        . = ALIGN(4);
+    } >rom
+
     /* Put the stack at the bottom of RAM, so that the application will
      * crash on stack overflow instead of silently corrupting memory.
      * See: http://blog.japaric.io/stack-overflow-protection/ */