Rust bindings: Use CARGO_MANIFEST_DIR in build.rs
When a rust crate uses the boringssl rust bindings like:
```Cargo.toml
[dependencies]
bssl-sys = { path = "./third_party/boringssl/build/rust" }
```
The working directory of `build.rs` is set to the the crate's
working directory so "." and ".." aren't relative to the bindings'
directory. Use CARGO_MANIFEST_DIR to specify link search paths.
Change-Id: Ieb49f4ab479f47390388dc5ace70561f593dc238
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/51645
Reviewed-by: David Drysdale <drysdale@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
diff --git a/.gitignore b/.gitignore
index 6cbc9d2..1a27c89 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,7 @@
*.swo
doc/*.html
doc/doc.css
+rust/Cargo.lock
rust/target
util/bot/android_ndk
