Vendor dependencies

Let's see how I like this workflow.

vendor/cxx/tools/buck/rust_cxx_bridge.bzl

@@ -0,0 +1,32 @@
+def rust_cxx_bridge(name, src, deps = []):
+    native.genrule(
+        name = "%s/header" % name,
+        out = src + ".h",
+        cmd = "cp $(location :%s/generated)/generated.h ${OUT}" % name,
+    )
+
+    native.genrule(
+        name = "%s/source" % name,
+        out = src + ".cc",
+        cmd = "cp $(location :%s/generated)/generated.cc ${OUT}" % name,
+    )
+
+    native.genrule(
+        name = "%s/generated" % name,
+        srcs = [src],
+        out = ".",
+        cmd = "$(exe //:codegen) ${SRCS} -o ${OUT}/generated.h -o ${OUT}/generated.cc",
+        type = "cxxbridge",
+    )
+
+    native.cxx_library(
+        name = name,
+        srcs = [":%s/source" % name],
+        preferred_linkage = "static",
+        exported_deps = deps + [":%s/include" % name],
+    )
+
+    native.cxx_library(
+        name = "%s/include" % name,
+        exported_headers = [":%s/header" % name],
+    )