[llvm] [cmake] Fix semicolon expansion when passing LLVM_TABLEGEN_FLAGS (PR #169518)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `sanitizer-ppc64le-linux` running on `ppc64le-sanitizer` while building `llvm` at step 2 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/72/builds/16547

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

```
Step 2 (annotate) failure: 'python ../sanitizer_buildbot/sanitizers/zorg/buildbot/builders/sanitizers/buildbot_selector.py' (failure) (timed out)
...
--------------------------------------------------------------------------

Testing Time: 1743.79s

Total Discovered Tests: 4637
  Excluded         : 1995 (43.02%)
  Skipped          :   13 (0.28%)
  Unsupported      :  516 (11.13%)
  Passed           : 2090 (45.07%)
  Expectedly Failed:   23 (0.50%)
command timed out: 1800 seconds without output running [b'python', b'../sanitizer_buildbot/sanitizers/zorg/buildbot/builders/sanitizers/buildbot_selector.py'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=4048.955005
Step 9 (test compiler-rt debug) failure: test compiler-rt debug (failure)
...
338.91s: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/ScudoCombinedDeathTestBasicCombined18_AndroidConfig/BasicCombined18
338.74s: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/ScudoCombinedDeathTestBasicCombined19_TestConditionVariableConfig/BasicCombined19
338.73s: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/ScudoCombinedDeathTestBasicCombined18_DefaultConfig/BasicCombined18
336.96s: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/ScudoCombinedDeathTestBasicCombined18_TestConditionVariableConfig/BasicCombined18
336.90s: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/ScudoCombinedDeathTestBasicCombined20_AndroidConfig/BasicCombined20
336.21s: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/ScudoCombinedDeathTestBasicCombined20_DefaultConfig/BasicCombined20
329.86s: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/ScudoCombinedDeathTestBasicCombined17_TestNoCacheConfig/BasicCombined17
328.31s: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/ScudoCombinedDeathTestBasicCombined17_TestConditionVariableConfig/BasicCombined17
327.90s: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/ScudoCombinedDeathTestBasicCombined17_AndroidConfig/BasicCombined17
323.21s: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/ScudoCombinedDeathTestBasicCombined17_DefaultConfig/BasicCombined17
322.65s: ScudoStandalone-Unit :: ./ScudoCxxUnitTest-powerpc64le-Test/ScudoWrappersCppDeathTest/New

Tests Times:
--------------------------------------------------------------------------
[   Range   ] :: [               Percentage               ] :: [  Count  ]
--------------------------------------------------------------------------
[900s,950s) :: [                                        ] :: [   1/2044]
[850s,900s) :: [                                        ] :: [   0/2044]
[800s,850s) :: [                                        ] :: [   0/2044]
[750s,800s) :: [                                        ] :: [   0/2044]
[700s,750s) :: [                                        ] :: [   0/2044]
[650s,700s) :: [                                        ] :: [   1/2044]
[600s,650s) :: [                                        ] :: [   0/2044]
[550s,600s) :: [                                        ] :: [   0/2044]
[500s,550s) :: [                                        ] :: [   0/2044]
[450s,500s) :: [                                        ] :: [   0/2044]
[400s,450s) :: [                                        ] :: [   0/2044]
[350s,400s) :: [                                        ] :: [   1/2044]
[300s,350s) :: [                                        ] :: [  39/2044]
[250s,300s) :: [***                                     ] :: [ 190/2044]
[200s,250s) :: [                                        ] :: [  22/2044]
[150s,200s) :: [                                        ] :: [   3/2044]
[100s,150s) :: [                                        ] :: [   3/2044]
[ 50s,100s) :: [                                        ] :: [  32/2044]
[  0s, 50s) :: [**********************************      ] :: [1752/2044]
--------------------------------------------------------------------------

Testing Time: 1743.79s

Total Discovered Tests: 4637
  Excluded         : 1995 (43.02%)
  Skipped          :   13 (0.28%)
  Unsupported      :  516 (11.13%)
  Passed           : 2090 (45.07%)
  Expectedly Failed:   23 (0.50%)

command timed out: 1800 seconds without output running [b'python', b'../sanitizer_buildbot/sanitizers/zorg/buildbot/builders/sanitizers/buildbot_selector.py'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=4048.955005

```

</details>

https://github.com/llvm/llvm-project/pull/169518