Vendor dependencies

Let's see how I like this workflow.

vendor/cxx/Cargo.toml

@@ -0,0 +1,89 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+rust-version = "1.48"
+name = "cxx"
+version = "1.0.85"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+links = "cxxbridge1"
+exclude = [
+    "/demo",
+    "/gen",
+    "/syntax",
+    "/third-party",
+]
+description = "Safe interop between Rust and C++"
+homepage = "https://cxx.rs"
+documentation = "https://docs.rs/cxx"
+readme = "README.md"
+keywords = [
+    "ffi",
+    "c++",
+]
+categories = [
+    "development-tools::ffi",
+    "api-bindings",
+    "no-std",
+]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/dtolnay/cxx"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+rustdoc-args = [
+    "--cfg",
+    "doc_cfg",
+]
+
+[lib]
+doc-scrape-examples = false
+
+[dependencies.cxxbridge-macro]
+version = "=1.0.85"
+
+[dependencies.link-cplusplus]
+version = "1.0"
+
+[dev-dependencies.cxx-build]
+version = "=1.0.85"
+
+[dev-dependencies.cxx-gen]
+version = "0.7"
+
+[dev-dependencies.cxx-test-suite]
+version = "0"
+
+[dev-dependencies.rustversion]
+version = "1.0"
+
+[dev-dependencies.trybuild]
+version = "1.0.66"
+features = ["diff"]
+
+[build-dependencies.cc]
+version = "1.0.49"
+
+[build-dependencies.cxxbridge-flags]
+version = "=1.0.85"
+default-features = false
+
+[features]
+alloc = []
+"c++14" = ["cxxbridge-flags/c++14"]
+"c++17" = ["cxxbridge-flags/c++17"]
+"c++20" = ["cxxbridge-flags/c++20"]
+default = [
+    "std",
+    "cxxbridge-flags/default",
+]
+std = ["alloc"]