HADOOP-18214. Update BUILDING.txt (#3811)

java-8-openjdk become openjdk-8-jdk (see both ubuntu and debian package's name)

Contributed by Giovambattista Vieri
Reviewed-by: Ayush Saxena <ayushsaxena@apache.org>

Change-Id: I63b2bbfdd575cf56d20cd6c8fff33a70cadda7f2

BUILDING.txt

@@ -57,7 +57,7 @@ Installing required packages for clean install of Ubuntu 14.04 LTS Desktop:
   $ sudo apt-get install software-properties-common
   $ sudo add-apt-repository ppa:webupd8team/java
   $ sudo apt-get update
-  $ sudo apt-get install oracle-java8-installer
+  $ sudo apt-get -y install openjdk-8-jdk
 * Maven
   $ sudo apt-get -y install maven
 * Native libraries