Add script for updating libfuzzer from upstream.

README.md

@@ -48,6 +48,12 @@ $ cargo rustc -- -C passes='sancov' -C llvm-args='-sanitizer-coverage-level=3' -
 $ ./target/debug/fuzzed # runs fuzzing
 ```
 
+## Updating libfuzzer from upstream
+
+```
+./update-libfuzzer.sh <llvm/compiler-rt SHA1>
+```
+
 ## License
 
 All files in `libfuzzer` directory are licensed NCSA.

update-libfuzzer.sh

@@ -0,0 +1,10 @@
+#!/bin/bash -ex
+
+project_dir="$(pwd)"
+tmp_dir="$(mktemp -d)"
+
+git clone https://github.com/llvm-mirror/compiler-rt.git "$tmp_dir"
+cd "$tmp_dir"
+git checkout "$1"
+rm -rf "$project_dir/libfuzzer/"
+mv "$tmp_dir/lib/fuzzer/" "$project_dir/libfuzzer/"