runtime: improve Windows gdb tests

This ensures that gdb tests run on Windows by ignoring any line ending.

Works with gdb 7.7, however with gdb 7.9 and 7.12 gets an error
error:

    internal-error: buildsym_init: Assertion `free_pendings == NULL'
    failed.

Updates #21380

Change-Id: I6a6e5b2a1b5efdca4dfce009fcb9c134c87497d6
Reviewed-on: https://go-review.googlesource.com/102419
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

src/runtime/runtime-gdb_test.go

@@ -70,7 +70,7 @@ func checkGdbPython(t *testing.T) {
 	if err != nil {
 		t.Skipf("skipping due to issue running gdb: %v", err)
 	}
-	if string(out) != "go gdb python support\n" {
+	if strings.TrimSpace(string(out)) != "go gdb python support" {
 		t.Skipf("skipping due to lack of python gdb support: %s", out)
 	}
 }
@@ -154,8 +154,8 @@ func testGdbPython(t *testing.T, cgo bool) {
 		t.Fatalf("building source %v\n%s", err, out)
 	}
 
-	args := []string{"-nx", "-q", "--batch", "-iex",
-		fmt.Sprintf("add-auto-load-safe-path %s/src/runtime", runtime.GOROOT()),
+	args := []string{"-nx", "-q", "--batch",
+		"-iex", "add-auto-load-safe-path " + filepath.Join(runtime.GOROOT(), "src", "runtime"),
 		"-ex", "set startup-with-shell off",
 		"-ex", "info auto-load python-scripts",
 		"-ex", "set python print-stack full",
@@ -320,6 +320,7 @@ func TestGdbBacktrace(t *testing.T) {
 
 	// Execute gdb commands.
 	args := []string{"-nx", "-batch",
+		"-iex", "add-auto-load-safe-path " + filepath.Join(runtime.GOROOT(), "src", "runtime"),
 		"-ex", "set startup-with-shell off",
 		"-ex", "break main.eee",
 		"-ex", "run",
@@ -390,6 +391,7 @@ func TestGdbAutotmpTypes(t *testing.T) {
 
 	// Execute gdb commands.
 	args := []string{"-nx", "-batch",
+		"-iex", "add-auto-load-safe-path " + filepath.Join(runtime.GOROOT(), "src", "runtime"),
 		"-ex", "set startup-with-shell off",
 		"-ex", "break main.main",
 		"-ex", "run",
@@ -455,6 +457,7 @@ func TestGdbConst(t *testing.T) {
 
 	// Execute gdb commands.
 	args := []string{"-nx", "-batch",
+		"-iex", "add-auto-load-safe-path " + filepath.Join(runtime.GOROOT(), "src", "runtime"),
 		"-ex", "set startup-with-shell off",
 		"-ex", "break main.main",
 		"-ex", "run",