[llvm] [CMake][CAS] Do not export CASPluginTest from the install tree (PR #215292)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lldb-aarch64-ubuntu` running on `linaro-lldb-aarch64-ubuntu` while building `llvm` at step 6 "test".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/59/builds/36494

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test) failure: build (failure)
...
PASS: lldb-unit :: tools/lldb-mcp/./LLDBMCPTests/2/12 (2694 of 2704)
PASS: lldb-unit :: Host/./HostTests/8/12 (2695 of 2704)
PASS: lldb-unit :: Host/./HostTests/9/12 (2696 of 2704)
PASS: lldb-unit :: Target/./TargetTests/4/8 (2697 of 2704)
PASS: lldb-unit :: Target/./TargetTests/5/8 (2698 of 2704)
PASS: lldb-unit :: Host/./HostTests/0/12 (2699 of 2704)
PASS: lldb-unit :: Host/./HostTests/1/12 (2700 of 2704)
PASS: lldb-unit :: Process/gdb-remote/./ProcessGdbRemoteTests/8/11 (2701 of 2704)
PASS: lldb-unit :: Process/gdb-remote/./ProcessGdbRemoteTests/9/11 (2702 of 2704)
TIMEOUT: lldb-api :: tools/lldb-dap/breakpoint/TestDAP_setBreakpoints.py (2703 of 2704)
******************** TEST 'lldb-api :: tools/lldb-dap/breakpoint/TestDAP_setBreakpoints.py' FAILED ********************
Script:
--
/usr/bin/python3.10 /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/dotest.py -u CXXFLAGS -u CFLAGS --env LLVM_LIBS_DIR=/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./lib --env LLVM_INCLUDE_DIR=/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/include --env LLVM_TOOLS_DIR=/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin --triple aarch64-unknown-linux-gnu --build-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build --lldb-module-cache-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build/module-cache-lldb/lldb-api --clang-module-cache-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build/module-cache-clang/lldb-api --executable /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin/lldb --lldb-python-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/local/lib/python3.10/dist-packages --compiler /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin/clang --dsymutil /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin/dsymutil --make /usr/bin/gmake --llvm-tools-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin --lldb-obj-root /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/tools/lldb --lldb-libs-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./lib --cmake-build-type Release /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/tools/lldb-dap/breakpoint -p TestDAP_setBreakpoints.py
--
Exit Code: -9
Timeout: Reached timeout of 600 seconds

Command Output (stdout):
--
Skipping the following test categories: libc++, msvcstl, dsym, pdb, gmodules, debugserver, objc

--
Command Output (stderr):
--
PASS: LLDB (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang-aarch64) :: test_clear_breakpoints_unset_breakpoints (TestDAP_setBreakpoints.TestDAP_setBreakpoints)
FAIL: LLDB (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang-aarch64) :: test_column_breakpoints (TestDAP_setBreakpoints.TestDAP_setBreakpoints)
Log Files:
 - /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build/tools/lldb-dap/breakpoint/TestDAP_setBreakpoints.test_column_breakpoints/Error_test_column_breakpoints.log
PASS: LLDB (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang-aarch64) :: test_functionality (TestDAP_setBreakpoints.TestDAP_setBreakpoints)
PASS: LLDB (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang-aarch64) :: test_hit_multiple_breakpoints (TestDAP_setBreakpoints.TestDAP_setBreakpoints)
PASS: LLDB (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang-aarch64) :: test_set_and_clear (TestDAP_setBreakpoints.TestDAP_setBreakpoints)
PASS: LLDB (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang-aarch64) :: test_source_map (TestDAP_setBreakpoints.TestDAP_setBreakpoints)
======================================================================
ERROR: test_column_breakpoints (TestDAP_setBreakpoints.TestDAP_setBreakpoints)
   Test setting multiple breakpoints in the same line at different columns.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/lldbtest.py", line 1211, in tearDown
    hook()  # try the plain call and hope it works
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/tools/lldb_dap/testcase.py", line 114, in cleanup_session
    session.disconnect(terminateDebuggee=True)
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/tools/lldb_dap/session_helpers.py", line 1718, in disconnect
    response = self.send_request(args).result()
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/tools/lldb_dap/session.py", line 99, in result
    response = self.result_or_error()
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/tools/lldb_dap/session.py", line 116, in result_or_error
    raw = self._future.result(timeout=self._timeout)
  File "/usr/lib/python3.10/concurrent/futures/_base.py", line 460, in result

```

</details>

https://github.com/llvm/llvm-project/pull/215292