cmd/link: enable internal linker in more cases for ppc64le

The internal linker is capable of linking the ppc64le linux
race detector and approved cgo packages.

Likewise, ppc64/linux and ppc64/aix do not support the race
detector. Thus, extra code to enforce external linking when
using the race detector on ppc64/ppc64le can be removed
entirely.

Fixes #21961

Change-Id: I10db14f65ee616ee3291e17409e8333e3af7d4df
Reviewed-on: https://go-review.googlesource.com/c/go/+/304459
Run-TryBot: Paul Murphy <murp@ibm.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

Author: pmur

src/cmd/dist/test.go

@@ -984,11 +984,6 @@ func (t *tester) internalLink() bool {
 		// linkmode=internal fails on dragonfly since errno is a TLS relocation.
 		return false
 	}
-	if gohostarch == "ppc64le" {
-		// linkmode=internal fails on ppc64le because cmd/link doesn't
-		// handle the TOC correctly (issue 15409).
-		return false
-	}
 	if goos == "android" {
 		return false
 	}

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

@@ -195,8 +195,7 @@ func mustLinkExternal(ctxt *Link) (res bool, reason string) {
 
 	// Internally linking cgo is incomplete on some architectures.
 	// https://golang.org/issue/14449
-	// https://golang.org/issue/21961
-	if iscgo && ctxt.Arch.InFamily(sys.MIPS64, sys.MIPS, sys.PPC64, sys.RISCV64) {
+	if iscgo && ctxt.Arch.InFamily(sys.MIPS64, sys.MIPS, sys.RISCV64) {
 		return true, buildcfg.GOARCH + " does not support internal cgo"
 	}
 	if iscgo && (buildcfg.GOOS == "android" || buildcfg.GOOS == "dragonfly") {
@@ -209,12 +208,9 @@ func mustLinkExternal(ctxt *Link) (res bool, reason string) {
 		// windows/arm64 internal linking is not implemented.
 		return true, buildcfg.GOOS + "/" + buildcfg.GOARCH + " does not support internal cgo"
 	}
-
-	// When the race flag is set, the LLVM tsan relocatable file is linked
-	// into the final binary, which means external linking is required because
-	// internal linking does not support it.
-	if *flagRace && ctxt.Arch.InFamily(sys.PPC64) {
-		return true, "race on " + buildcfg.GOARCH
+	if iscgo && ctxt.Arch == sys.ArchPPC64 {
+		// Big Endian PPC64 cgo internal linking is not implemented for aix or linux.
+		return true, buildcfg.GOOS + " does not support internal cgo"
 	}
 
 	// Some build modes require work the internal linker cannot do (yet).