fix Issue 13117 - Executable size of hello world explodes from 472K to 2.7M

- This problem seems to stem from mixed writeable flags for the
  .deh/.minfo sections in PIC/non-PIC code. The ld.bfd linker would
  still try to bracket the sections, even though it previously mapped
  them to different segments, thereby creating one huge segment which
  contains all read-only and all writeable data plus the big hole in
  between them.

- fixed by always marking those sections as writeable

[Issue 13117](https://issues.dlang.org/show_bug.cgi?id=13117 "Executable size of hello world explodes from 472K to 2.7M")