Introduce CTS_SRC_ROOT classpath variable for cts-tradefed.

Use a Eclipse classpath variable to locate cts-tradefed dependent jars,
instead of linking them as separate Eclipse projects. This change
will make it easier to switch between cts branches under development.

Change-Id: I6f4b5e36aba90f1c2bc9f346ae84cfa2c5cae481
diff --git a/tools/tradefed-host/.classpath b/tools/tradefed-host/.classpath
index 197543c..275ecf9 100644
--- a/tools/tradefed-host/.classpath
+++ b/tools/tradefed-host/.classpath
@@ -6,7 +6,7 @@
 	<classpathentry kind="con" path="org.eclipse.jdt.junit.JUNIT_CONTAINER/3"/>
 	<classpathentry combineaccessrules="false" kind="src" path="/ddmlib"/>
 	<classpathentry combineaccessrules="false" kind="src" path="/tradefederation"/>
-	<classpathentry combineaccessrules="false" kind="src" path="/hosttestlib"/>
-	<classpathentry combineaccessrules="false" exported="true" kind="src" path="/ctsdeviceinfolib"/>
+	<classpathentry exported="true" kind="var" path="CTS_SRC_ROOT/out/host/common/obj/JAVA_LIBRARIES/ctsdeviceinfolib_intermediates/javalib.jar"/>
+	<classpathentry exported="true" kind="var" path="CTS_SRC_ROOT/out/host/common/obj/JAVA_LIBRARIES/hosttestlib_intermediates/javalib.jar"/>
 	<classpathentry kind="output" path="bin"/>
 </classpath>