bazel: Add initial config for binary distribution (see #3757)

Add support for building the CEF binary distribution using Bazel
and the default platform toolchain. Tested to work for Windows
x64, MacOS ARM64 and x64 (cross-compile from ARM64), and
Linux x64. Windows x86 (cross-compile from x64) is known to
be broken, see https://github.com/bazelbuild/bazel/issues/22164.

Includes minor changes to tests directory structure to meet
Bazel build requirements.

bazel/linux/variables.bzl

@@ -0,0 +1,68 @@
+# Copyright (c) 2024 The Chromium Embedded Framework Authors. All rights
+# reserved. Use of this source code is governed by a BSD-style license that
+# can be found in the LICENSE file.
+
+#
+# Distribution SOs.
+#
+
+SOS = [
+    "libcef.so",
+    "libEGL.so",
+    "libGLESv2.so",
+    "libvk_swiftshader.so",
+    "libvulkan.so.1",
+]
+
+#
+# Common 'linkopts' for cc_binary targets.
+#
+
+# Standard link libraries.
+STANDARD_LIBS = [
+    "X11",
+]
+
+COMMON_LINKOPTS_DEBUG = [
+]
+
+COMMON_LINKOPTS_RELEASE = [
+]
+
+COMMON_LINKOPTS = [
+    "-l{}".format(lib) for lib in STANDARD_LIBS
+]  + select({
+    "//:linux_dbg": COMMON_LINKOPTS_DEBUG,
+    "//conditions:default": COMMON_LINKOPTS_RELEASE,
+})
+
+#
+# Common 'copts' for cc_libary and cc_binary targets.
+#
+
+COMMON_COPTS = [
+]
+
+COMMON_COPTS_DEBUG = [
+]
+
+COMMON_COPTS_RELEASE = [
+]
+
+#
+# Common 'defines' for cc_libary targets.
+#
+
+COMMON_DEFINES = [
+    # Used by apps to test if the sandbox is enabled
+    "CEF_USE_SANDBOX",
+]
+
+COMMON_DEFINES_DEBUG = [
+]
+
+COMMON_DEFINES_RELEASE = [
+    # Not a debug build
+    "NDEBUG",
+]
+