Move linux to //third_party.

Test Plan: refactor of build system, should be covered by existing tests

X-Origin-Diff: phab/D367
GitOrigin-RevId: 603c61bfadadfbd66c0ce31f05f6748251bea9f3
diff --git a/third_party/linux/BUILD.bazel b/third_party/linux/BUILD.bazel
new file mode 100644
index 0000000..3829f96
--- /dev/null
+++ b/third_party/linux/BUILD.bazel
@@ -0,0 +1,22 @@
+genrule(
+    name = "bzImage",
+    srcs = [
+        "@linux//:all",
+        "linux-smalltown.config",
+    ],
+    outs = [
+        "bzImage",
+    ],
+    cmd = """
+    DIR=external/linux
+
+    mkdir $$DIR/.bin
+
+    cp $(location linux-smalltown.config) $$DIR/.config
+
+    (cd $$DIR && make -j $$(nproc) >/dev/null)
+
+    cp $$DIR/arch/x86/boot/bzImage $(RULEDIR)
+    """,
+    visibility = ["//visibility:public"],
+)