THRIFT-450. java: Propagate CLASSPATH from ./configure to make and ant

- Put "AC_SUBST(CLASSPATH)" configure.ac so the CLASSPATH used to run
  ./configure is passed in to make.
- Put "export CLASSPATH" in lib/java/Makefile.am so that the CLASSPATH
  passed to make is passed to ant.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@777678 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/java/Makefile.am b/lib/java/Makefile.am
index ffcdc03..c5c7521 100644
--- a/lib/java/Makefile.am
+++ b/lib/java/Makefile.am
@@ -19,6 +19,8 @@
 
 EXTRA_DIST = build.xml src test
 
+export CLASSPATH
+
 all-local:
 	$(ANT) $(ANT_FLAGS)