update readme for ubuntu sudo java_home behavior (#1013)

README.md

@@ -131,6 +131,8 @@ Currently, the following distributions are supported:
 
 **NOTE:** Oracle JDK 17 licensing varies by patch level. As shown on the [JDK 17 Archive](https://www.oracle.com/java/technologies/javase/jdk17-archive-downloads.html) (versions up to 17.0.12 are under the [NFTC](https://www.oracle.com/downloads/licenses/no-fee-license.html) license) and the [JDK 17.0.13+ Archive](https://www.oracle.com/java/technologies/javase/jdk17-0-13-later-archive-downloads.html) (versions 17.0.13 and later are under the [OTN](https://www.oracle.com/downloads/licenses/javase-license1.html) license). To stay on the free NFTC license, use `distribution: 'oracle'` with `java-version: '17.0.12'` (or earlier) instead of the floating `'17'`. Alternatively, upgrade to Oracle JDK 21+, which remains under the NFTC license.
 
+**NOTE:** On Ubuntu runners, commands executed via `sudo` do not inherit the `JAVA_HOME` and `PATH` set by `setup-java` and will fall back to the runner image's system-default JDK.
+
 ### Caching packages dependencies
 The action has a built-in functionality for caching and restoring dependencies. It uses [toolkit/cache](https://github.com/actions/toolkit/tree/main/packages/cache) under hood for caching dependencies but requires less configuration settings. Supported package managers are gradle, maven and sbt. The format of the used cache key is `setup-java-${{ platform }}-${{ packageManager }}-${{ fileHash }}`, where the hash is based on the following files: