cmd/internal/ld: recompute resoff after changing elfreserve

My last update to https://golang.org/cl/9710 missed this.

Change-Id: Ie042032ca307e1065fcf6c402a166f9ff74027e7
Reviewed-on: https://go-review.googlesource.com/9771Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/ld/elf.go

@@ -1928,6 +1928,7 @@ func Asmbelf(symo int64) {
 			// in the intermediate object file, not the final shared
 			// library.
 			elfreserve *= 3
+			resoff = elfreserve
 			sh := elfshname(".note.go.pkg-list")
 			resoff -= int64(elfgopkgnote(sh, uint64(startva), uint64(resoff)))
 		}