This Driver/lock_interface.swift test has been
spontaenously failing for the past few days.
I've decided to disable it until an investigation
and fix can happen.
rdar://82261445
Testing that the compiler rebuilds the same module more than once with
-disable-interface-lock was not reliable as some jobs could be executed
after the module was rebuilt. Just make sure the compiler accepts the
flag :/
When rebuilding a module interface from the textual interface, lock the
destination path of the created swiftmodule instead of the source
swiftinterface. The swiftinterface files are likely to be in the SDK and
may be on a read-only filesystem.
rdar://60247977
This ensures only one process is generating module cache from an interface
file so that we don't blow up memory usage when multiple processes are
doing the same. The locking mechanism is similar to that of Clang's.
A better approach is that the build system takes care of the module building
step as a formal dependency.
rdar://52839445
