Use Bazel Preconditions variant which avoids varargs array creation

Reduces garbage.

--
MOS_MIGRATED_REVID=109914243
diff --git a/src/main/java/com/google/devtools/build/skyframe/SkyKey.java b/src/main/java/com/google/devtools/build/skyframe/SkyKey.java
index 6e8ec87..482940d 100644
--- a/src/main/java/com/google/devtools/build/skyframe/SkyKey.java
+++ b/src/main/java/com/google/devtools/build/skyframe/SkyKey.java
@@ -14,7 +14,7 @@
 package com.google.devtools.build.skyframe;
 
 import com.google.common.base.Function;
-import com.google.common.base.Preconditions;
+import com.google.devtools.build.lib.util.Preconditions;
 
 import java.io.Serializable;