[doc] Add tips for building fluss with Java 8 (apache#1177)

Author: leonardBang

website/community/dev/building.md

@@ -29,6 +29,11 @@ In order to build Fluss you need to get the source code by [clone the git reposi
 
 In addition, you need **Maven 3.8.6** and a **JDK** (Java Development Kit). Fluss requires **Java 8 or Java 11** to build.
 
+:::tip
+- It is recommended to use JDK 1.8.3 if you're using Java 8 and encounter an error like `java.lang.NoSuchMethodError: 'java.nio.MappedByteBuffer java.nio.MappedByteBuffer.duplicate()'`.
+- Setting the environment variable via `export JAVA_TOOL_OPTIONS="-XX:+UnlockExperimentalVMOptions"` is useful if you encounter an error `VM option 'UseG1GC' is experimental and must be enabled via -XX:+UnlockExperimentalVMOptions`.
+:::
+
 To clone from git, enter:
 
 ```bash