[compiler-rt][cmake] Change orc-rt target names (#216901)

When configured with `LLVM_ENABLE_RUNTIMES=compiler-rt;orc-rt`,
following two CMake errors occur.

```
CMake Error at llvm-project/llvm/cmake/modules/AddLLVM.cmake:2245 (add_custom_target):
  add_custom_target cannot create target "check-orc-rt" because another
  target with the same name already exists.  The existing target is a custom
  target created in source directory
  "llvm-project/compiler-rt/test/orc".  See documentation
  for policy CMP0002 for more details.
Call Stack (most recent call first):
  llvm-project/llvm/cmake/modules/AddLLVM.cmake:2326 (add_lit_target)
  llvm-project/orc-rt/test/CMakeLists.txt:24 (add_lit_testsuite)

CMake Error at llvm-project/orc-rt/test/unit/CMakeLists.txt:1 (add_custom_target):
  add_custom_target cannot create target "OrcRTUnitTests" because another
  target with the same name already exists.  The existing target is a custom
  target created in source directory
  "llvm-project/compiler-rt/lib/orc/tests".  See
  documentation for policy CMP0002 for more details.
```

Both `compiler-rt/lib/orc/tests/CMakeLists.txt` and
`orc-rt/test/unit/CMakeLists.txt` define targets named `OrcRTUnitTests`.
Both `compiler-rt/test/orc/CMakeLists.txt` and
`orc-rt/test/CMakeLists.txt` define targets named `check-orc-rt`.

This commit changes target names in compiler-rt.

GitOrigin-RevId: 86440cce63c88ca5491320ae72d43db9964c83f2