Docs: Replacing 12.04 Ubuntu with 14.04

Bug: 18959029
Change-Id: Ib4245b69b8262bc1f917ebf4ad74d0a06ab00255
diff --git a/src/source/building.jd b/src/source/building.jd
index e6f5849..a0c3985 100644
--- a/src/source/building.jd
+++ b/src/source/building.jd
@@ -17,7 +17,7 @@
     limitations under the License.
 -->
 <p>The Android build is routinely tested in-house on recent versions of
-Ubuntu LTS (12.04), but most distributions should have the required
+Ubuntu LTS (14.04), but most distributions should have the required
 build tools available. We welcome reports of successes or failures on other
 distributions.</p>