[stubs] Prevent CMake from linking with object lib

[modocache]

Attempting to link against an object library results in a CMake error. Prevent such an error by removing a line I mistakenly added in b86125a.

[jrose-apple]

Ah, is that where the Linux-only error we've been seeing came from? @shahmishal

[shahmishal]

@jrose-apple Yes, looks like it.

[jrose-apple]

@swift-ci Please test Linux platform

[jrose-apple]

@swift-ci Please smoke test OS X platform

[modocache]

Ah, is that where the Linux-only error we've been seeing came from?

Yes, my apologies! 🙇

[swift-ci]

Build failed
Jenkins build - Swift Test Linux Platform
Git Commit - 49248a4
Test requested by - @jrose-apple

[modocache]

The test failure on Linux appears unrelated. More importantly, the Linux build of the runtime succeeded, which indicates the patch works as expected.

[jrose-apple]

Yeah, we need to get this in. @swift-ci Please smoke test

[modocache]

@jrose-apple Smoke test appears to have passed. Sorry again for the build break! 😞

[gottesmm]

@jrose-apple I am going to merge this since it passed the tests and you said it "needs to get in".