[boringssl] Update prerequisites for Rust bindgen

Change-Id: I936e272711524c05fc10cb73b19f106158a672f1
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/boringssl/+/468334
Commit-Queue: Ali Zhang <alizhang@google.com>
Reviewed-by: Darren Krahn <dkrahn@google.com>
Fuchsia-Auto-Submit: Ali Zhang <alizhang@google.com>
diff --git a/README.fuchsia b/README.fuchsia
index ed3dca1..7a28e24 100644
--- a/README.fuchsia
+++ b/README.fuchsia
@@ -9,7 +9,7 @@
 A fork of OpenSSL, as described at https://www.imperialviolet.org/2014/06/20/boringssl.html
-* apt install curl git golang perl python
+* apt install curl git golang perl python llvm-dev libclang-dev clang
 * curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
 To update: