recover from exception on iOS and macOS using signals and log the stacktrace

src/objc_utils.h

@@ -1,8 +1,6 @@
 #pragma once
 
 #ifdef __OBJC__
-
-
 @interface PathWithModDate : NSObject
 @property (strong) NSString *path;
 @property (strong) NSDate *modDate;
@@ -10,6 +8,6 @@
 
 @interface ObjcUtils : NSObject
 @end
-
-
 #endif
+
+void install_global_handlers();