Fix missing include for use_gold.

Change-Id: I60096b0e70049d490ba8bd3c7514f19e8de0017b
Reviewed-on: https://swiftshader-review.googlesource.com/9951
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index b04b321..52a78e8 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -12,6 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import("//build/config/compiler/compiler.gni")
+
 config("swiftshader_config") {
   defines = [ "STRICT_CONFORMANCE" ]  # Disables OpenGL ES 3.0