Fix CFI buildbot: import chrome_build.gni for is_official_build.

build/config/sanitizers/BUILD.gn

Index: build/config/sanitizers/BUILD.gn
diff --git a/build/config/sanitizers/BUILD.gn b/build/config/sanitizers/BUILD.gn
index 2ae03044cae2e36e380077d89d159ece3076a8f0..2adab21f21602e5aa4487540c0889770505e5658 100644
--- a/build/config/sanitizers/BUILD.gn
+++ b/build/config/sanitizers/BUILD.gn
@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/chrome_build.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
 # Contains the dependencies needed for sanitizers to link into executables and
@@ -37,6 +38,7 @@ config("sanitizer_options_link_helper") {
   if (is_msan) {
     ldflags += [
       "-fsanitize=memory",
+
       # TODO(eugenis): Remove when msan migrates to new ABI (crbug.com/560589).
       "-pie",
     ]
@@ -142,6 +144,7 @@ config("default_sanitizer_flags") {
         "-fsanitize=memory",
         "-fsanitize-memory-track-origins=$msan_track_origins",
         "-fsanitize-blacklist=$msan_blacklist_path",
+
         # TODO(eugenis): Remove when msan migrates to new ABI (crbug.com/560589).
         "-fPIC",
       ]