Revert "[ORC] Add unit tests for parts of the Orc and LLJIT C APIs."

This reverts commit 8740360.

This commit caused failures on some builders (see e.g.
https://lab.llvm.org/buildbot/#/builders/5/builds/7071). Reverting while I
investigate.

Author: lhames

llvm/unittests/ExecutionEngine/Orc/CMakeLists.txt

@@ -17,7 +17,6 @@ add_llvm_unittest(OrcJITTests
   IndirectionUtilsTest.cpp
   JITTargetMachineBuilderTest.cpp
   LazyCallThroughAndReexportsTest.cpp
-  OrcCAPITest.cpp
   OrcTestCommon.cpp
   QueueChannel.cpp
   ResourceTrackerTest.cpp