dev-rust/bindgen: Add ebuild for bindgen binary and dependencies.

This provides the bindgen executable for use with scripts that generate
Rust bindings. It also adds the dependencies required to build bindgen
v0.56.0.

BUG=chromium:1156506
TEST=./build_packages --board=${BOARD} dev-rust/bindgen

Change-Id: If891aa96f62c0d461f79bffb53dbfc0c568d3821
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/2578151
Tested-by: Allen Webb <allenwebb@google.com>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Commit-Queue: Allen Webb <allenwebb@google.com>
diff --git a/dev-rust/regex-syntax/Manifest b/dev-rust/regex-syntax/Manifest
index 5aeba5a..022e4f1 100644
--- a/dev-rust/regex-syntax/Manifest
+++ b/dev-rust/regex-syntax/Manifest
@@ -1 +1,2 @@
+DIST regex-syntax-0.6.21.crate 293572 BLAKE2B 49c499ba1c03447fe7c90f27147dc5d96daf815e330a4073fe293d3be594fab1d798d35a5e49f6af43c71befd47528927246c4ebb24b6a6a141135484bbecd31 SHA512 56507f4432804ea30820984f6cff03c3514988bc3e406b3ba3a89c36c9c5d75951e4acd000ba85b95bb83d253898ce7d7d282ed930e811e12bb644c4a5ec84fa
 DIST regex-syntax-0.6.5.crate 272475 BLAKE2B b2ff299b4b87ab91c925a10faa8a09507272600a12558cade5b18ce615844223384e8420f2025dbd642bf80acb5f608a6c0f5ca59a4c391d4f417fdea15058b0 SHA512 37f2c69b425335a28b8945fcd58a3a39a9adde5588fdcd4b460da0fbd137e0727a7835d71b4e87ff29185c153379402891847d93047e40a578f778a62b324f5d