Fix zlib build by adding src folder to includes

uncompr.c tries to include src/zlib.h but references it as "zlib.h".

Change-Id: I8c4a7c697a26cc4af9399669459e794533e012fe
diff --git a/BUILD b/BUILD
index 96d9d92..2320e53 100644
--- a/BUILD
+++ b/BUILD
@@ -45,5 +45,8 @@
         "-Wno-unused-variable",
         "-Wno-implicit-function-declaration",
     ],
+    includes = [
+        "src"
+    ],
     visibility = ["//visibility:public"],
 )