[llvm] [llvm] Remove `br i1 undef` from regression tests (PR #117292)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

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

Full details are available at: https://lab.llvm.org/buildbot/#/builders/18/builds/7606

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

```
Step 6 (test) failure: build (failure)
...
PASS: lldb-api :: functionalities/dyld-exec-linux/TestDyldExecLinux.py (442 of 2839)
UNSUPPORTED: lldb-api :: functionalities/fat_archives/TestFatArchives.py (443 of 2839)
PASS: lldb-api :: functionalities/executable_first/TestExecutableFirst.py (444 of 2839)
PASS: lldb-api :: functionalities/dynamic_value_child_count/TestDynamicValueChildCount.py (445 of 2839)
PASS: lldb-api :: functionalities/find-line-entry/TestFindLineEntry.py (446 of 2839)
UNSUPPORTED: lldb-api :: functionalities/fork/concurrent_vfork/TestConcurrentVFork.py (447 of 2839)
PASS: lldb-api :: functionalities/exec/TestExec.py (448 of 2839)
PASS: lldb-api :: functionalities/gdb_remote_client/TestAArch64XMLRegOffsets.py (449 of 2839)
PASS: lldb-api :: functionalities/float-display/TestFloatDisplay.py (450 of 2839)
PASS: lldb-api :: functionalities/gdb_remote_client/TestArmRegisterDefinition.py (451 of 2839)
FAIL: lldb-api :: functionalities/fork/resumes-child/TestForkResumesChild.py (452 of 2839)
******************** TEST 'lldb-api :: functionalities/fork/resumes-child/TestForkResumesChild.py' FAILED ********************
Script:
--
/usr/bin/python3.10 /home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/lldb/test/API/dotest.py -u CXXFLAGS -u CFLAGS --env LLVM_LIBS_DIR=/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/./lib --env LLVM_INCLUDE_DIR=/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/include --env LLVM_TOOLS_DIR=/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/./bin --arch armv8l --build-dir /home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/lldb-test-build.noindex --lldb-module-cache-dir /home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/lldb-test-build.noindex/module-cache-lldb/lldb-api --clang-module-cache-dir /home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/lldb-test-build.noindex/module-cache-clang/lldb-api --executable /home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/./bin/lldb --compiler /home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/./bin/clang --dsymutil /home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/./bin/dsymutil --make /usr/bin/make --llvm-tools-dir /home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/./bin --lldb-obj-root /home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/tools/lldb --lldb-libs-dir /home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/./lib /home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/lldb/test/API/functionalities/fork/resumes-child -p TestForkResumesChild.py
--
Exit Code: 1

Command Output (stdout):
--
lldb version 20.0.0git (https://github.com/llvm/llvm-project.git revision cefc1b0c211fcc3f5528b72d5883f0c390d63e71)
  clang revision cefc1b0c211fcc3f5528b72d5883f0c390d63e71
  llvm revision cefc1b0c211fcc3f5528b72d5883f0c390d63e71
Skipping the following test categories: ['libc++', 'dsym', 'gmodules', 'debugserver', 'objc']

--
Command Output (stderr):
--
FAIL: LLDB (/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/bin/clang-arm) :: test_step_over_fork (TestForkResumesChild.TestForkResumesChild)
======================================================================
FAIL: test_step_over_fork (TestForkResumesChild.TestForkResumesChild)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/lldb/test/API/functionalities/fork/resumes-child/TestForkResumesChild.py", line 22, in test_step_over_fork
    self.expect("continue", substrs=["exited with status = 0"])
  File "/home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/lldbtest.py", line 2370, in expect
    self.runCmd(
  File "/home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/lldbtest.py", line 1000, in runCmd
    self.assertTrue(self.res.Succeeded(), msg + output)
AssertionError: False is not true : Command 'continue' did not return successfully
Error output:
error: Process must be launched.

Config=arm-/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/bin/clang
----------------------------------------------------------------------
Ran 1 test in 0.809s

FAILED (failures=1)


```

</details>

https://github.com/llvm/llvm-project/pull/117292