pkg/build: better support for gvisor race build

Explicitly pass --features=race.
Expect linux_amd64_static_stripped as a potential output.

pkg/build/gvisor.go

@@ -6,28 +6,29 @@ package build
 import (
 	"fmt"
 	"path/filepath"
+	"strings"
 	"time"
 
 	"github.com/google/syzkaller/pkg/osutil"
 )
 
 type gvisor struct{}
 
-func (gvisor) build(targetArch, vmType, kernelDir, outputDir, compiler, userspaceDir,
+func (gvisor gvisor) build(targetArch, vmType, kernelDir, outputDir, compiler, userspaceDir,
 	cmdlineFile, sysctlFile string, config []byte) error {
 	if err := osutil.MkdirAll(outputDir); err != nil {
 		return err
 	}
-	if _, err := osutil.RunCmd(20*time.Minute, kernelDir, compiler, "build", "--verbose_failures", "runsc"); err != nil {
+	args := []string{"build", "--verbose_failures"}
+	if strings.Contains(" "+string(config)+" ", " -race ") {
+		args = append(args, "--features=race")
+	}
+	args = append(args, "runsc")
+	if _, err := osutil.RunCmd(20*time.Minute, kernelDir, compiler, args...); err != nil {
 		return err
 	}
-	// Funny it's not possible to understand what bazel actually built...
-	runsc := filepath.Join(kernelDir, "bazel-bin", "runsc", "linux_amd64_pure_stripped", "runsc")
-	if err := osutil.CopyFile(runsc, filepath.Join(outputDir, "image")); err != nil {
-		runsc = filepath.Join(kernelDir, "bazel-bin", "runsc", "linux_amd64_static_race_stripped", "runsc")
-		if err := osutil.CopyFile(runsc, filepath.Join(outputDir, "image")); err != nil {
-			return err
-		}
+	if err := gvisor.copyBinary(kernelDir, outputDir); err != nil {
+		return err
 	}
 	if len(config) != 0 {
 		if err := osutil.WriteFile(filepath.Join(outputDir, "kernel.config"), config); err != nil {
@@ -38,6 +39,22 @@ func (gvisor) build(targetArch, vmType, kernelDir, outputDir, compiler, userspac
 	return nil
 }
 
+func (gvisor) copyBinary(kernelDir, outputDir string) error {
+	// Funny it's not possible to understand what bazel actually built...
+	for _, typ := range []string{
+		"linux_amd64_pure_stripped",
+		"linux_amd64_static_stripped",
+		"linux_amd64_static_race_stripped",
+	} {
+		runsc := filepath.Join(kernelDir, "bazel-bin", "runsc", typ, "runsc")
+		if !osutil.IsExist(runsc) {
+			continue
+		}
+		return osutil.CopyFile(runsc, filepath.Join(outputDir, "image"))
+	}
+	return fmt.Errorf("failed to locate bazel output")
+}
+
 func (gvisor) clean(kernelDir string) error {
 	// Let's assume that bazel always properly handles build without cleaning (until proven otherwise).
 	return nil