cmd/link: enable PIE on darwin/arm

We used to pass -no_pie to external linker on darwin/arm, which
is incompatible with -fembed-bitcode. CL 201358 attempted to
remove the -no_pie flag, but it resulted the darwin linker to
complain about absolute addressing in TEXT segment.

On darwin/arm, we already get away from absolute addressing in
the TEXT section. The complained absolute addressing is in
RODATA, which was embedded in the TEXT segment. This CL moves
RODATA to the DATA segment, like what we already did on ARM64
and on AMD64 in c-archive/c-shared buildmodes for the same reason.
So there is no absolute addressing in the TEXT segment, which
allows us to remove -no_pie flag.

Fixes #35252.
Updates #32963.

Change-Id: Id6e3a594cb066d257d4f58fadb4a3ee4672529f7
Reviewed-on: https://go-review.googlesource.com/c/go/+/205060Reviewed-by: Elias Naur <mail@eliasnaur.com>

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

@@ -1209,10 +1209,8 @@ func (ctxt *Link) hostlink() {
 	switch ctxt.BuildMode {
 	case BuildModeExe:
 		if ctxt.HeadType == objabi.Hdarwin {
-			if ctxt.Arch.Family != sys.ARM64 {
-				argv = append(argv, "-Wl,-no_pie")
-			}
 			if !ctxt.Arch.InFamily(sys.ARM, sys.ARM64) {
+				argv = append(argv, "-Wl,-no_pie")
 				argv = append(argv, "-Wl,-pagezero_size,4000000")
 			}
 		}

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

@@ -488,9 +488,9 @@ func machoshbits(ctxt *Link, mseg *MachoSeg, sect *sym.Section, segname string)
 
 	var msect *MachoSect
 	if sect.Rwx&1 == 0 && segname != "__DWARF" && (ctxt.Arch.Family == sys.ARM64 ||
-		(ctxt.Arch.Family == sys.AMD64 && ctxt.BuildMode != BuildModeExe) ||
-		(ctxt.Arch.Family == sys.ARM && ctxt.BuildMode != BuildModeExe)) {
-		// Darwin external linker on arm64 and on amd64 and arm in c-shared/c-archive buildmode
+		ctxt.Arch.Family == sys.ARM ||
+		(ctxt.Arch.Family == sys.AMD64 && ctxt.BuildMode != BuildModeExe)) {
+		// Darwin external linker on arm and arm64, and on amd64 in c-shared/c-archive buildmode
 		// complains about absolute relocs in __TEXT, so if the section is not
 		// executable, put it in __DATA segment.
 		msect = newMachoSect(mseg, buf, "__DATA")