I have been seeing occasional errors building the JDK similar to the following:

```
build/support/gensrc/java.desktop/sun/awt/AWTIcon64_security_icon_yellow24_png.java:4: error: illegal start of expression
[0.010s][warning][perf,memops] Cannot use file /tmp/hsperfdata_... because it is locked by another process (errno = 11)
^
```

The tool that generates e.g. AWTIcon64_security_icon_yellow24_png.java has -Xlog output to stdout enabled, and the log output ends up in the output file for the tool.

I think the build logic for this specific is here:

* https://github.com/openjdk/jdk/blob/0db47028913b64b84116d912876c58b136a9f70c/make/modules/java.desktop/gensrc/GensrcIcons.gmk#L73
* https://github.com/openjdk/jdk/blob/0db47028913b64b84116d912876c58b136a9f70c/make/ToolsJdk.gmk#L104-L105

Per https://openjdk.org/jeps/158

> The default configuration is that all messages using warning and error level are output to stderr.

However the actual implementation was changed to default to stdout in JDK-8153723. There's some related discussion in JDK-8272121, JDK-8357014.

I've seen this cause a number of similar issues in other tools, which pipe stdout to a file and get broken if the JVM happens to log anything to stdout while they're running.

One fix would be to update the -Xlog implementation to implement the stderr default described in JEP-158.

Otherwise the OpenJDK build may want to explicitly configure logging to stderr using ` -Xlog:disable -Xlog:all=warning:stderr`, for TOOL_AWT_TOBIN and other similar tools that pipe stdout to a file.