lld: work around elftoolchain bug which causes bloated RISCV binaries

The elftoolchain strip(1) command appears to have trouble with the new
.riscv.attributes sections being added by lld 17 to RISCV binaries. This
causes huge 'holes' in the files, making them larger than necessary.

Since nothing in the base system uses the new section yet, patch lld to
leave it out for now.

Direct commit to stable/13, since this intended to go into the 13.3
release, while the elftoolchain bug is being investigated.

Reported by: karels
Submitted by: jrtc27
Approved by: re (cperciva)