As .rodata isn't one of the default created sections for COFF, it was
created as a read-write data section. By using the default .rdata
section name for COFF, it automatically becomes a read-only data section.
The existing ".section .rodata" works as intended for ELF though.

This is based on an original patch and diagnose by Tom Tan
<Tom.Tan@microsoft.com>.
Signed-off-by: Martin Storsjö <martin@martin.st>