HADOOP-8722. Update BUILDING.txt with latest snappy info. Contributed by Colin Patrick McCabe

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1379282 13f79535-47bb-0310-9956-ffa450edef68

BUILDING.txt

@@ -54,12 +54,32 @@ Maven build goals:
  Build options:
 
   * Use -Pnative to compile/bundle native code
-  * Use -Dsnappy.prefix=(/usr/local) & -Dbundle.snappy=(false) to compile
-    Snappy JNI bindings and to bundle Snappy SO files
   * Use -Pdocs to generate & bundle the documentation in the distribution (using -Pdist)
   * Use -Psrc to create a project source TAR.GZ
   * Use -Dtar to create a TAR with the distribution (using -Pdist)
 
+ Snappy build options:
+
+   Snappy is a compression library that can be utilized by the native code.
+   It is currently an optional component, meaning that Hadoop can be built with
+   or without this dependency.
+
+  * Use -Drequire.snappy to fail the build if libsnappy.so is not found.
+    If this option is not specified and the snappy library is missing,
+    we silently build a version of libhadoop.so that cannot make use of snappy.
+    This option is recommended if you plan on making use of snappy and want
+    to get more repeatable builds.
+
+  * Use -Dsnappy.prefix to specify a nonstandard location for the libsnappy
+    header files and library files. You do not need this option if you have
+    installed snappy using a package manager.
+  * Use -Dsnappy.lib to specify a nonstandard location for the libsnappy library
+    files.  Similarly to snappy.prefix, you do not need this option if you have
+    installed snappy using a package manager.
+  * Use -Dbundle.snappy to copy the contents of the snappy.lib directory into
+    the final tar file. This option requires that -Dsnappy.lib is also given,
+    and it ignores the -Dsnappy.prefix option.
+
    Tests options:
 
   * Use -DskipTests to skip tests when running the following Maven goals:

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -249,6 +249,9 @@ Release 2.0.1-alpha - UNRELEASED
 
     HADOOP-8747. Syntax error on cmake version 2.6 patch 2 in JNIFlags.cmake. (cmccabe via tucu)
 
+    HADOOP-8722. Update BUILDING.txt with latest snappy info.
+    (Colin Patrick McCabe via eli)
+
   BREAKDOWN OF HDFS-3042 SUBTASKS
 
     HADOOP-8220. ZKFailoverController doesn't handle failure to become active