tools/docker: install bazelisk instead of bazel

The needed Bazel version to build gVisor got bumped. However, instead of
doing the same bump in two places whenever this happens, we can simply
use bazelisk in syzkaller to determine which bazel version to use
automatically.

Author: konstantin-s-bogom

pkg/build/build.go

@@ -192,7 +192,7 @@ func compilerIdentity(compiler string) (string, error) {
 	arg, timeout := "--version", time.Minute
 	if bazel {
 		// Bazel episodically fails with 1 min timeout.
-		arg, timeout = "", 10*time.Minute
+		timeout = 10 * time.Minute
 	}
 	output, err := osutil.RunCmd(timeout, "", compiler, arg)
 	if err != nil {
@@ -210,6 +210,9 @@ func compilerIdentity(compiler string) (string, error) {
 			if strings.HasPrefix(line, "WARNING: ") {
 				continue
 			}
+			if strings.Contains(line, "Downloading https://releases.bazel") {
+				continue
+			}
 		}
 
 		return strings.TrimSpace(line), nil

tools/docker/syzbot/Dockerfile

@@ -61,9 +61,12 @@ RUN apt-get install -y -q --no-install-recommends clang-15
 # Not really GRTE, but it's enough to run some scripts that hardcode the path.
 RUN mkdir -p /usr/grte/v5/bin && ln -s /usr/bin/python3 /usr/grte/v5/bin/python2.7
 
-# Install bazel
-# Download the official bazel binary. The APT repository isn't used because there is not packages for arm64.
-RUN sh -c 'curl -o /usr/local/bin/bazel https://releases.bazel.build/7.1.2/release/bazel-7.1.2-linux-$(uname -m | sed s/aarch64/arm64/) && chmod ugo+x /usr/local/bin/bazel'
+# Install bazelisk
+RUN curl -s https://api.github.com/repos/bazelbuild/bazelisk/releases/latest \
+        | sed -n '/browser_download_url/s/[^:]*:[^"]*\("[^"]*"\).*/url = \1/p' \
+        | grep bazelisk-linux-$(uname -m | sed s/aarch64/arm64/ | sed s/x86_64/amd64/) \
+        | curl -L -o /usr/local/bin/bazel -K - \
+        && chmod +x /usr/local/bin/bazel
 
 # Install qemu from the backports.
 # The currently stable version (7.2) cannot properly run arm64-MTE kernels.