[release-branch.go1.20] cmd/link: suppress -bind_at_load deprecation warning for ld-prime

ld-prime emits a deprecation warning for -bind_at_load. The flag
is needed for plugins to not deadlock (#38824) when linking with
older darwin linker. It is supposedly not needed with newer linker
when chained fixups are used. For now, we always pass it, and
suppress the warning.

Updates #61229.
For #62597.

Change-Id: I4b8a6f864a460c40dc38adbb533f664f7fd5343c
Reviewed-on: https://go-review.googlesource.com/c/go/+/508696
Reviewed-by: Than McIntosh <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Cherry Mui <[email protected]>
(cherry picked from commit 040dbf9)
Reviewed-on: https://go-review.googlesource.com/c/go/+/527798

Author: cherrymui

src/cmd/link/internal/ld/lib.go

@@ -1842,6 +1842,16 @@ func (ctxt *Link) hostlink() {
 				out = append(out[:i], out[i+len(noPieWarning):]...)
 			}
 		}
+		if ctxt.IsDarwin() {
+			const bindAtLoadWarning = "ld: warning: -bind_at_load is deprecated on macOS\n"
+			if i := bytes.Index(out, []byte(bindAtLoadWarning)); i >= 0 {
+				// -bind_at_load is deprecated with ld-prime, but needed for
+				// correctness with older versions of ld64. Swallow the warning.
+				// TODO: maybe pass -bind_at_load conditionally based on C
+				// linker version.
+				out = append(out[:i], out[i+len(bindAtLoadWarning):]...)
+			}
+		}
 		ctxt.Logf("%s", out)
 	}