[lld] [LLD][COFF] Require explicit specification of ARM64EC target (PR #116281)

[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 `lld` at step 6 "test".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/18/builds/7484

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

```
Step 6 (test) failure: build (failure)
...
PASS: lldb-api :: commands/frame/recognizer/TestFrameRecognizer.py (164 of 2839)
UNSUPPORTED: lldb-api :: commands/gui/expand-threads-tree/TestGuiExpandThreadsTree.py (165 of 2839)
PASS: lldb-api :: commands/gui/invalid-args/TestInvalidArgsGui.py (166 of 2839)
UNSUPPORTED: lldb-api :: commands/gui/viewlarge/TestGuiViewLarge.py (167 of 2839)
PASS: lldb-api :: commands/help/TestHelp.py (168 of 2839)
PASS: lldb-api :: commands/log/basic/TestLogHandlers.py (169 of 2839)
PASS: lldb-api :: commands/log/invalid-args/TestInvalidArgsLog.py (170 of 2839)
PASS: lldb-api :: commands/memory/write/TestMemoryWrite.py (171 of 2839)
PASS: lldb-api :: commands/memory/read/TestMemoryRead.py (172 of 2839)
UNRESOLVED: lldb-api :: commands/gui/spawn-threads/TestGuiSpawnThreads.py (173 of 2839)
******************** TEST 'lldb-api :: commands/gui/spawn-threads/TestGuiSpawnThreads.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/commands/gui/spawn-threads -p TestGuiSpawnThreads.py
--
Exit Code: 1

Command Output (stdout):
--
lldb version 20.0.0git (https://github.com/llvm/llvm-project.git revision f942949a7cf16a082eb43943b2a4f93f9180556f)
  clang revision f942949a7cf16a082eb43943b2a4f93f9180556f
  llvm revision f942949a7cf16a082eb43943b2a4f93f9180556f
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_gui (TestGuiSpawnThreads.TestGuiSpawnThreadsTest)
======================================================================
ERROR: test_gui (TestGuiSpawnThreads.TestGuiSpawnThreadsTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/decorators.py", line 148, in wrapper
    return func(*args, **kwargs)
  File "/home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/lldb/test/API/commands/gui/spawn-threads/TestGuiSpawnThreads.py", line 44, in test_gui
    self.child.expect_exact(f"thread #{i + 2}: tid =")
  File "/usr/local/lib/python3.10/dist-packages/pexpect/spawnbase.py", line 432, in expect_exact
    return exp.expect_loop(timeout)
  File "/usr/local/lib/python3.10/dist-packages/pexpect/expect.py", line 179, in expect_loop
    return self.eof(e)
  File "/usr/local/lib/python3.10/dist-packages/pexpect/expect.py", line 122, in eof
    raise exc
pexpect.exceptions.EOF: End Of File (EOF). Exception style platform.
<pexpect.pty_spawn.spawn object at 0xe95dbfa0>
command: /home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/bin/lldb
args: ['/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/bin/lldb', '--no-lldbinit', '--no-use-colors', '-O', 'settings clear -all', '-O', 'settings set symbols.enable-external-lookup false', '-O', 'settings set target.inherit-tcc true', '-O', 'settings set target.disable-aslr false', '-O', 'settings set target.detach-on-error false', '-O', 'settings set target.auto-apply-fixits false', '-O', 'settings set plugin.process.gdb-remote.packet-timeout 60', '-O', 'settings set symbols.clang-modules-cache-path "/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/lldb-test-build.noindex/module-cache-lldb/lldb-api"', '-O', 'settings set use-color false', '--file', '/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/lldb-test-build.noindex/commands/gui/spawn-threads/TestGuiSpawnThreads.test_gui/a.out']
buffer (last 100 chars): b''
before (last 100 chars): b'p/lit-tmp-jkuc6sro/diagnostics-5cf2d0\nPlease include the directory content when filing a bug report\n'
after: <class 'pexpect.exceptions.EOF'>

```

</details>

https://github.com/llvm/llvm-project/pull/116281