gold/
* options.h (General_options): Add -Trodata-segment option.
* parameters.cc (Parameters::check_rodata_segment): New function.
(Parameters::set_target_once): Call it.
* parameters.h (Parameters): Declare it (private member function).
* layout.cc (load_seg_unusable_for_headers): New function, broken
out of Layout::relaxation_loop_body. If TARGET->isolate_execinstr()
then validate rodata segment rather than text segment.
(relaxation_loop_body): Call that.
(is_text_segment): New function. Don't admit a non-executable
segment if TARGET->isolate_execinstr().
(set_segment_offsets): Call it. Honor -Trodata-segment option.