specify bazel version + more tests

add these toolchains:
1. toolchain-free (on-host gcc)
2. llvm without sysroot

results/hyperfine.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+set -x
+
+exec hyperfine \
+    --export-markdown=results/hyperfine.md \
+    --runs 5 \
+    -L toolchain ,--extra_toolchains=@llvm_toolchain//:cc-toolchain-x86_64-linux,--extra_toolchains=@llvm_toolchain_with_sysroot//:cc-toolchain-x86_64-linux,--platforms=@zig_sdk//libc_aware/platform:linux_amd64_gnu.2.28 \
+    -L sandbox_strategy "--spawn_strategy=local,--spawn_strategy=sandboxed --experimental_reuse_sandbox_directories,--spawn_strategy=sandboxed" \
+    -p "bazel build {toolchain} {sandbox_strategy} //:zigzag-0; bazel clean; bazel shutdown" \
+       "bazel build {toolchain} {sandbox_strategy} //..."