Thanks Adrian!
That said, my bridging header is 2 lines long actually:
#import "Application.h"
#import "CrashReportingSchedulerObjC.h"
and Application.h defines a single ObjC class with a single @import of UIKit, and CrashReportingSchedulerObjC.h has protocol + class definitions with two @import-s of Foundation and Crashlytics.
FWIW, I've just replaced a legacy #import <Foundation/Foundation.h> with modern @import Foundation; and improved breakpoint time by 18 seconds, so now it takes 43 seconds, which is better, but its still 43 seconds on non-incremental non-clean build app start.
@Adrian_Prantl Could you please elaborate a bit more for me. What is Clang dependency? If that is ObjC code, then I currently have 3 ObjC files in main target (I've mentioned two above + main.m), and the main target is the only one that has SWIFT_OBJC_BRIDGING_HEADER set. I can try to move that code off the main target to a separate framework, is this what you mean by 'modularizing as much of your Clang dependencies as possible'?
UPD:
I've completely removed bridging header and wiped SWIFT_OBJC_BRIDGING_HEADER build setting, leaving a single non-swift file main.m in my main target, but it is still 43 seconds.