Add a sanity check on the conscrypt contents.

To diagnose current buildbot issues.

Test: buildbot-build.sh
Change-Id: I3aba09cfd1feda49e785f16931905e120327afa8
diff --git a/tools/buildbot-build.sh b/tools/buildbot-build.sh
index bac0e13..142918f 100755
--- a/tools/buildbot-build.sh
+++ b/tools/buildbot-build.sh
@@ -162,6 +162,10 @@
     echo -e "Missing conscrypt APEX in build output: ${conscrypt_dir}"
     exit 1
   fi
+  if [ ! -f "${conscrypt_dir}/javalib/conscrypt.jar" ]; then
+    echo -e "Missing conscrypt jar in build output: ${conscrypt_dir}"
+    exit 1
+  fi
   for l in lib lib64; do
     if [ ! -d "$ANDROID_PRODUCT_OUT/system/$l" ]; then
       continue