Remove unneeded pcrecpp dependency.

BUG=None
TEST=emerge-link -av1 update_engine built without issue.

Change-Id: I1287c808fa363f42cff71ba22684b600cf164722
Reviewed-on: https://gerrit.chromium.org/gerrit/66381
Reviewed-by: Chris Sosa <sosa@chromium.org>
Tested-by: Andrew de los Reyes <adlr@chromium.org>
Commit-Queue: Andrew de los Reyes <adlr@chromium.org>
diff --git a/SConstruct b/SConstruct
index 9d34cd4..dc4dd6c 100644
--- a/SConstruct
+++ b/SConstruct
@@ -203,7 +203,6 @@
                        gflags
                        glib-2.0
                        gthread-2.0
-                       libpcrecpp
                        metrics
                        policy-%s
                        protobuf