cmd/dist: use -buildmode=pie for pie testing

Some tests in misc/cgo/test are run with various options including
'-linkmode=external "-extldflags=-pie"'. On ppc64x passing -pie to
the external linker with code that was not compiled as position
independent is incorrect. This works by luck in many cases but is
not guaranteed to work. I suspect it is an issue on other targets
as well.

This will now run the tests using -buildmode=pie for the platforms
that support that buildmode option.

Fixes #21954

Change-Id: I25fc7573f2d3cb5b0d1c691a0ac91aef7715404f
Reviewed-on: https://go-review.googlesource.com/66870
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/dist/test.go

@@ -837,6 +837,16 @@ func (t *tester) supportedBuildmode(mode string) bool {
 			return true
 		}
 		return false
+	case "pie":
+		switch pair {
+		case "linux-386", "linux-amd64", "linux-arm", "linux-arm64", "linux-ppc64le", "linux-s390x",
+			"android-amd64", "android-arm", "android-arm64", "android-386":
+			return true
+		case "darwin-amd64":
+			return true
+		}
+		return false
+
 	default:
 		log.Fatalf("internal error: unknown buildmode %s", mode)
 		return false
@@ -902,33 +912,10 @@ func (t *tester) cgoTest(dt *distTest) error {
 			// static linking on FreeBSD/ARM with clang. (cgo depends on
 			// -fPIC fundamentally.)
 		default:
-			cmd := t.dirCmd("misc/cgo/test",
-				defaultcc, "-xc", "-o", "/dev/null", "-static", "-")
-			cmd.Stdin = strings.NewReader("int main() {}")
-			if err := cmd.Run(); err != nil {
-				fmt.Println("No support for static linking found (lacks libc.a?), skip cgo static linking test.")
-			} else {
-				if goos != "android" {
-					t.addCmd(dt, "misc/cgo/testtls", "go", "test", "-ldflags", `-linkmode=external -extldflags "-static -pthread"`)
-				}
-				t.addCmd(dt, "misc/cgo/nocgo", "go", "test")
-				t.addCmd(dt, "misc/cgo/nocgo", "go", "test", "-ldflags", `-linkmode=external`)
-				if goos != "android" {
-					t.addCmd(dt, "misc/cgo/nocgo", "go", "test", "-ldflags", `-linkmode=external -extldflags "-static -pthread"`)
-				}
-			}
-
-			if pair != "freebsd-amd64" { // clang -pie fails to link misc/cgo/test
-				cmd := t.dirCmd("misc/cgo/test",
-					defaultcc, "-xc", "-o", "/dev/null", "-pie", "-")
-				cmd.Stdin = strings.NewReader("int main() {}")
-				if err := cmd.Run(); err != nil {
-					fmt.Println("No support for -pie found, skip cgo PIE test.")
-				} else {
-					t.addCmd(dt, "misc/cgo/test", "go", "test", "-ldflags", `-linkmode=external -extldflags "-pie"`)
-					t.addCmd(dt, "misc/cgo/testtls", "go", "test", "-ldflags", `-linkmode=external -extldflags "-pie"`)
-					t.addCmd(dt, "misc/cgo/nocgo", "go", "test", "-ldflags", `-linkmode=external -extldflags "-pie"`)
-				}
+			if t.supportedBuildmode("pie") {
+				t.addCmd(dt, "misc/cgo/test", "go", "test", "-buildmode=pie")
+				t.addCmd(dt, "misc/cgo/testtls", "go", "test", "-buildmode=pie")
+				t.addCmd(dt, "misc/cgo/nocgo", "go", "test", "-buildmode=pie")
 			}
 		}
 	}