Vendor dependencies

Let's see how I like this workflow.

vendor/cxx/tools/buck/prelude/toolchains/cxx.bzl

@@ -0,0 +1,107 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under both the MIT license found in the
+# LICENSE-MIT file in the root directory of this source tree and the Apache
+# License, Version 2.0 found in the LICENSE-APACHE file in the root directory
+# of this source tree.
+
+load(
+    "@prelude//cxx:cxx_toolchain_types.bzl",
+    "BinaryUtilitiesInfo",
+    "CCompilerInfo",
+    "CxxCompilerInfo",
+    "CxxPlatformInfo",
+    "CxxToolchainInfo",
+    "LinkerInfo",
+)
+load(
+    "@prelude//cxx:headers.bzl",
+    "HeaderMode",
+)
+load(
+    "@prelude//linking:link_info.bzl",
+    "LinkStyle",
+)
+
+def _system_cxx_toolchain_impl(ctx):
+    """
+    A very simple toolchain that is hardcoded to the current environment.
+    """
+    archiver_type = "gnu"
+    linker_type = "gnu"
+    if host_info().os.is_macos:
+        linker_type = "darwin"
+    elif host_info().os.is_windows:
+        linker_type = "windows"
+        archiver_type = "windows"
+    return [
+        DefaultInfo(),
+        CxxToolchainInfo(
+            mk_comp_db = ctx.attrs.make_comp_db,
+            linker_info = LinkerInfo(
+                linker = RunInfo(args = ["clang++"]),
+                linker_flags = [],
+                archiver = RunInfo(args = ["ar", "rcs"]),
+                archiver_type = archiver_type,
+                type = linker_type,
+                link_binaries_locally = True,
+                archive_objects_locally = True,
+                use_archiver_flags = False,
+                static_dep_runtime_ld_flags = [],
+                static_pic_dep_runtime_ld_flags = [],
+                shared_dep_runtime_ld_flags = [],
+                independent_shlib_interface_linker_flags = [],
+                shlib_interfaces = "disabled",
+                link_style = LinkStyle(ctx.attrs.link_style),
+                link_weight = 1,
+                binary_extension = "",
+                object_file_extension = "o",
+                shared_library_name_format = "lib{}.so",
+                shared_library_versioned_name_format = "lib{}.so.{}",
+                static_library_extension = "a",
+                force_full_hybrid_if_capable = False,
+            ),
+            bolt_enabled = False,
+            binary_utilities_info = BinaryUtilitiesInfo(
+                nm = RunInfo(args = ["nm"]),
+                # objcopy = ctx.attrs.objcopy_for_shared_library_interface[RunInfo],
+                # ranlib = ctx.attrs.ranlib[RunInfo],
+                ranlib = RunInfo(args = ["raninfo"]),
+                strip = RunInfo(args = ["strip"]),
+                dwp = None,
+                bolt_msdk = None,
+            ),
+            cxx_compiler_info = CxxCompilerInfo(
+                compiler = RunInfo(args = ["clang++"]),
+                preprocessor_flags = [],
+                compiler_flags = [],
+                compiler_type = "clang",  # one of CxxToolProviderType
+            ),
+            c_compiler_info = CCompilerInfo(
+                compiler = RunInfo(args = ["clang"]),
+                preprocessor_flags = [],
+                compiler_flags = [],
+                compiler_type = "clang",  # one of CxxToolProviderType
+            ),
+            as_compiler_info = CCompilerInfo(
+                compiler = RunInfo(args = ["clang"]),
+                compiler_type = "clang",  # one of CxxToolProviderType
+            ),
+            asm_compiler_info = CCompilerInfo(
+                compiler = RunInfo(args = ["clang"]),
+                compiler_type = "clang",  # one of CxxToolProviderType
+            ),
+            header_mode = HeaderMode("symlink_tree_only"),
+        ),
+        CxxPlatformInfo(name = "x86_64"),
+    ]
+
+# Use clang, since thats available everywhere and what we have tested with.
+system_cxx_toolchain = rule(
+    impl = _system_cxx_toolchain_impl,
+    attrs = {
+        "link_style": attrs.string(default = "shared"),
+        "make_comp_db": attrs.default_only(attrs.dep(providers = [RunInfo], default = "prelude//cxx/tools:make_comp_db")),
+    },
+    is_toolchain_rule = True,
+)