cmd/internal/objfile: recognize Mach-O __DATA_CONST segment as read-only data

Updates #38830.

Change-Id: I826c6b0a42bc8e48fcda556250ca4a95c73987eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/253918
Run-TryBot: Cherry Zhang <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>

Author: cherrymui

src/cmd/internal/objfile/macho.go

@@ -60,7 +60,7 @@ func (f *machoFile) symbols() ([]Sym, error) {
 		} else if int(s.Sect) <= len(f.macho.Sections) {
 			sect := f.macho.Sections[s.Sect-1]
 			switch sect.Seg {
-			case "__TEXT":
+			case "__TEXT", "__DATA_CONST":
 				sym.Code = 'R'
 			case "__DATA":
 				sym.Code = 'D'