[CMake] Don't add an extraneous rpath to the swift-frontend (#66121)

Cherrypick of #64103

Explanation: The current 5.9 snapshot has an incorrect relative runpath added to the compiler on linux, the second one:

```
> readelf -d swift-5.9-DEVELOPMENT-SNAPSHOT-2023-05-22-a-ubuntu20.04/usr/bin/swift-frontend | ag runpath
 0x000000000000001d (RUNPATH)            Library runpath: [$ORIGIN/../lib/swift/linux:$ORIGIN/../../lib/swift/linux]
This pull fixes that, removing a mild security risk when running the compiler.
```

Scope: Only affects the compiler runpath on linux

Issue: None

Risk: low, as it only removes an unused runpath for the linux compiler

Testing: Passed all CI on trunk

Reviewer: @edymtt

Author: finagolfin

tools/driver/CMakeLists.txt

@@ -73,8 +73,6 @@ target_link_libraries(swift-frontend
 
 add_swift_parser_link_libraries(swift-frontend)
 
-_add_swift_runtime_link_flags(swift-frontend "../../lib" "")
-
 # Create a `swift-driver` executable adjacent to the `swift-frontend` executable
 # to ensure that `swiftc` forwards to the standalone driver when invoked.
 swift_create_early_driver_copies(swift-frontend)