Include Swift module bridge_header to source in Xcode project

The bridge_header property of target building a Swift module
are considered source file. Ensure they are listed with the
other source files in the generated Xcode project.

Bug: none
Change-Id: I40d5660cb95b10e320e406464c13f30400520c6c
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/11880
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>

src/gn/xcode_writer.cc

diff --git a/src/gn/xcode_writer.cc b/src/gn/xcode_writer.cc
index 27f28e1..45fc378 100644
--- a/src/gn/xcode_writer.cc
+++ b/src/gn/xcode_writer.cc
@@ -647,6 +647,11 @@
         sources.insert(source);
     }
 
+    const SourceFile& bridge_header = target->swift_values().bridge_header();
+    if (!bridge_header.is_null() && ShouldIncludeFileInProject(bridge_header)) {
+      sources.insert(bridge_header);
+    }
+
     if (target->output_type() == Target::ACTION ||
         target->output_type() == Target::ACTION_FOREACH) {
       if (ShouldIncludeFileInProject(target->action_values().script()))