darwin/amd64: fix text-relocation issues for c-archive libraries

The existing implementation deals with absolute relocations in __TEXT
for darwin/amd64 in build-mode c-shared, but it ignores c-archive.
This results in issues when trying to use a c-archive in an iOS
app on the 64-bit simulator. This patch adds c-archive to the
handling of this issue.

Fixes #14217

Change-Id: I2e4d5193caa531171ad22fd0cd420a8bfb4646a6
Reviewed-on: https://go-review.googlesource.com/19206Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/22046

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

@@ -356,8 +356,9 @@ func machoshbits(mseg *MachoSeg, sect *Section, segname string) {
 	buf := "__" + strings.Replace(sect.Name[1:], ".", "_", -1)
 
 	var msect *MachoSect
-	if sect.Rwx&1 == 0 && (Thearch.Thechar == '7' || (Thearch.Thechar == '6' && Buildmode == BuildmodeCShared)) {
-		// Darwin external linker on arm64 and on amd64 in c-shared buildmode
+	if sect.Rwx&1 == 0 && (Thearch.Thechar == '7' || // arm64
+		(Thearch.Thechar == '6' && (Buildmode == BuildmodeCShared || Buildmode == BuildmodeCArchive))) { // amd64
+		// Darwin external linker on 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")