Xcode Instruments: Leaks - App crashes on launch
Actually I think this is a bug of Instruments. Try to use the Allocations template instead, then click + and add the Leaks tool.
I found my answer here, but only after discovering the "Console" view in Instruments, which included the following log message right after the app appeared to crash:
This copy of libswiftCore.dylib requires an OS version prior to 12.2.0
I used Xcode 10.2.1 and an iPad running iOS 12.4. So to reiterate the answer (credits to user msk):
If iOS >= 12.2, provide
/usr/lib/swiftas a first argument for Runpath Search Paths (under "Linking" in your Build Settings).