[llvm] [TableGen] Avoid assignmentInAssert warning (PR #139715)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-nvptx64-nvidia-ubuntu` running on `as-builder-7` while building `llvm` at step 6 "test-build-unified-tree-check-llvm".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/160/builds/17373

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

```
Step 6 (test-build-unified-tree-check-llvm) failure: test (failure)
******************** TEST 'LLVM :: TableGen/GlobalISelCombinerEmitter/type-inference.td' FAILED ********************
Exit Code: 134

Command Output (stderr):
--
/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/build/bin/llvm-tblgen -I /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/../../../include -gen-global-isel-combiner      -gicombiner-debug-typeinfer -combiners=MyCombiner /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/type-inference.td 2>&1 >/dev/null |  /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/build/bin/FileCheck /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/type-inference.td # RUN: at line 1
+ /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/build/bin/llvm-tblgen -I /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/../../../include -gen-global-isel-combiner -gicombiner-debug-typeinfer -combiners=MyCombiner /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/type-inference.td
+ /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/build/bin/FileCheck /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/type-inference.td
/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/build/test/TableGen/GlobalISelCombinerEmitter/Output/type-inference.td.script: line 1: 2722291 Aborted                 /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/build/bin/llvm-tblgen -I /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/../../../include -gen-global-isel-combiner -gicombiner-debug-typeinfer -combiners=MyCombiner /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/type-inference.td 2>&1 > /dev/null
     2722294 Done                    | /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/build/bin/FileCheck /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/test/TableGen/GlobalISelCombinerEmitter/type-inference.td

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/139715