cmd/link: Revert -buildmode=pie to internal linking

When internal linking was broken buildmode PIE is set to external
linking. Now internal linking is fixed, -buildmode=pie can default to
internal linking again.

Fixes #35545

Change-Id: Iaf86b3047eb76babebc1545a79125586a7a3980e
Reviewed-on: https://go-review.googlesource.com/c/go/+/207877
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

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

@@ -244,7 +244,7 @@ func determineLinkMode(ctxt *Link) {
 			ctxt.LinkMode = LinkExternal
 			via = "via GO_EXTLINK_ENABLED "
 		default:
-			if extNeeded || (iscgo && externalobj) || ctxt.BuildMode == BuildModePIE {
+			if extNeeded || (iscgo && externalobj) {
 				ctxt.LinkMode = LinkExternal
 			} else {
 				ctxt.LinkMode = LinkInternal