lto: Stream has_unroll flag during LTO [PR116140]

lto: Stream has_unroll flag during LTO [PR116140]

When #pragma GCC unroll is processed in
tree-cfg.cc:replace_loop_annotate_in_block, we set both the loop->unroll
field (which is currently streamed out and back in during LTO) but also
the cfun->has_unroll flag.

cfun->has_unroll, however, is not currently streamed during LTO.  This
patch fixes that.

Prior to this patch, loops marked with #pragma GCC unroll that would be
unrolled by RTL loop2_unroll in a non-LTO compilation didn't get
unrolled under LTO.

gcc/ChangeLog:

	PR libstdc++/116140
	* lto-streamer-in.cc (input_struct_function_base): Stream in
	fn->has_unroll.
	* lto-streamer-out.cc (output_struct_function_base): Stream out
	fn->has_unroll.

gcc/testsuite/ChangeLog:

	PR libstdc++/116140
	* g++.dg/ext/pragma-unroll-lambda-lto.C: New test.