cmd/link: fix suspicious code in emitPcln

In cmd/link/internal/ld/pcln.go:emitPcln, the code and the
comment don't match. I think the comment is right. Fix the code.

As a consequence, on Linux/AMD64, internal linking with PIE
buildmode with cgo (at least the cgo packages in the standard
library) now works. Add a test.

Change-Id: I091cf81ba89571052bc0ec1fa0a6a688dec07b04
Reviewed-on: https://go-review.googlesource.com/c/go/+/166017
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/dist/test.go

@@ -579,6 +579,17 @@ func (t *tester) registerTests() {
 				return nil
 			},
 		})
+		// Also test a cgo package.
+		if t.cgoEnabled {
+			t.tests = append(t.tests, distTest{
+				name:    "pie_internal_cgo",
+				heading: "internal linking of -buildmode=pie",
+				fn: func(dt *distTest) error {
+					t.addCmd(dt, "src", t.goTest(), "os/user", "-buildmode=pie", "-ldflags=-linkmode=internal", t.timeout(60))
+					return nil
+				},
+			})
+		}
 	}
 
 	// sync tests

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

@@ -182,10 +182,7 @@ func emitPcln(ctxt *Link, s *sym.Symbol) bool {
 	}
 	// We want to generate func table entries only for the "lowest level" symbols,
 	// not containers of subsymbols.
-	if s.Attr.Container() {
-		return true
-	}
-	return true
+	return !s.Attr.Container()
 }
 
 // pclntab initializes the pclntab symbol with