Fix non-standalone build.

//testing/fuzzers:utils is missing an include_dirs entry.

TBR=tsepez@chromium.org

Change-Id: Ia1359f9620f9cb8c79ddba13c654e1d2c809466d
Reviewed-on: https://pdfium-review.googlesource.com/c/50370
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

testing/fuzzers/BUILD.gn

diff --git a/testing/fuzzers/BUILD.gn b/testing/fuzzers/BUILD.gn
index 5deda55..5a7145b 100644
--- a/testing/fuzzers/BUILD.gn
+++ b/testing/fuzzers/BUILD.gn
@@ -74,6 +74,7 @@
   ]
 
   testonly = true
+  include_dirs = [ "../.." ]
 }
 
 template("pdfium_public_fuzzer") {