cmd/link: for -buildmode=exe pass -no-pie to external linker

On some systems the external linker defaults to PIE. On some systems
DT_TEXTREL does not work correctly. When both are true we have a bad
situation: any Go program built with the default buildmode (exe) that
uses external linking will fail to run. Fix this by passing -no-pie to
the external linker, if the option is supported.

Fixes #17847.

Change-Id: I9b5ff97825d8b7f494f96d29c4c04f72b53dbf4e
Reviewed-on: https://go-review.googlesource.com/33106
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

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

@@ -1134,21 +1134,16 @@ func (l *Link) hostlink() {
 		}
 	}
 
-	sanitizers := *flagRace
-
-	for _, flag := range ldflag {
-		if strings.HasPrefix(flag, "-fsanitize=") {
-			sanitizers = true
-		}
-	}
-
 	argv = append(argv, ldflag...)
 
-	if sanitizers {
-		// On a system where the toolchain creates position independent
-		// executables by default, tsan/msan/asan/etc initialization can
-		// fail. So we pass -no-pie here, but support for that flag is quite
-		// new and we test for its support first.
+	// When building a program with the default -buildmode=exe the
+	// gc compiler generates code requires DT_TEXTREL in a
+	// position independent executable (PIE). On systems where the
+	// toolchain creates PIEs by default, and where DT_TEXTREL
+	// does not work, the resulting programs will not run. See
+	// issue #17847. To avoid this problem pass -no-pie to the
+	// toolchain if it is supported.
+	if Buildmode == BuildmodeExe {
 		src := filepath.Join(*flagTmpdir, "trivial.c")
 		if err := ioutil.WriteFile(src, []byte{}, 0666); err != nil {
 			Errorf(nil, "WriteFile trivial.c failed: %v", err)