doc: add ASAN build instructions

Author: gengjiawen

BUILDING.md

@@ -28,6 +28,7 @@ file a new issue.
     * [Running Coverage](#running-coverage)
     * [Building the documentation](#building-the-documentation)
     * [Building a debug build](#building-a-debug-build)
+    * [Building an ASAN build](#building-an-asan-build)
     * [Troubleshooting Unix and macOS builds](#troubleshooting-unix-and-macos-builds)
   * [Windows](#windows)
     * [Prerequisites](#prerequisites)
@@ -491,6 +492,22 @@ $ gdb /opt/node-debug/node core.node.8.1535359906
 $ backtrace
 ```
 
+#### Building an ASAN build
+
+[ASAN](https://github.com/google/sanitizers) can help detect various memory
+related bugs. ASAN builds are currently only supported on linux.
+If you want to check it on Windows or macOS or you want a consistent toolchain
+on Linux, you can try [Docker](https://www.docker.com/products/docker-desktop)
+ (using an image like `gengjiawen/node-build:2020-02-14`).
+
+The `--debug` is not necessary and will slow down build and testing, but it can
+show clear stacktrace if ASAN hits an issue.
+
+``` console
+$  ./configure --debug --enable-asan && make -j4
+$ make test-only
+```
+
 #### Troubleshooting Unix and macOS builds
 
 Stale builds can sometimes result in `file not found` errors while building.