[lld] [LLD][COFF] Add support for ARM64EC import call thunks. (PR #107931)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-sve-vla` running on `linaro-g3-03` while building `lld` at step 7 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/17/builds/2598

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

```
Step 7 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'libFuzzer-aarch64-default-Linux :: sigusr.test' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 6: rm -rf /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp
+ rm -rf /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp
RUN: at line 7: mkdir -p /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp
+ mkdir -p /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp
RUN: at line 8: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/./bin/clang    -Wthread-safety -Wthread-safety-reference -Wthread-safety-beta   --driver-mode=g++ -O2 -gline-tables-only -fsanitize=address,fuzzer -I/home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/compiler-rt/lib/fuzzer  -Wthread-safety -Wthread-safety-reference -Wthread-safety-beta  /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/compiler-rt/test/fuzzer/SleepOneSecondTest.cpp -o /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp/LFSIGUSR
+ /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/./bin/clang -Wthread-safety -Wthread-safety-reference -Wthread-safety-beta --driver-mode=g++ -O2 -gline-tables-only -fsanitize=address,fuzzer -I/home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/compiler-rt/lib/fuzzer -Wthread-safety -Wthread-safety-reference -Wthread-safety-beta /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/compiler-rt/test/fuzzer/SleepOneSecondTest.cpp -o /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp/LFSIGUSR
RUN: at line 10: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp/LFSIGUSR 2> /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp/log & export PID=$!
+ export PID=1297756
+ PID=1297756
RUN: at line 11: sleep 2
+ sleep 2
+ /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp/LFSIGUSR
RUN: at line 12: kill -SIGUSR1 $PID
+ kill -SIGUSR1 1297756
RUN: at line 13: sleep 3
+ sleep 3
RUN: at line 14: cat /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp/log | FileCheck /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/compiler-rt/test/fuzzer/sigusr.test
+ cat /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/runtimes/runtimes-bins/compiler-rt/test/fuzzer/AARCH64DefaultLinuxConfig/Output/sigusr.test.tmp/log
+ FileCheck /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/compiler-rt/test/fuzzer/sigusr.test
/home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/compiler-rt/test/fuzzer/sigusr.test:17:8: error: CHECK: expected string not found in input
CHECK: INFO: libFuzzer: exiting as requested
       ^
<stdin>:7:49: note: scanning from here
INFO: signal received, trying to exit gracefully
                                                ^

Input file: <stdin>
Check file: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/compiler-rt/test/fuzzer/sigusr.test

-dump-input=help explains the following input dump.

Input was:
<<<<<<
          1: INFO: Running with entropic power schedule (0xFF, 100). 
          2: INFO: Seed: 2497399819 
          3: INFO: Loaded 1 modules (4 inline 8-bit counters): 4 [0xaaaaace3ce98, 0xaaaaace3ce9c),  
          4: INFO: Loaded 1 PC tables (4 PCs): 4 [0xaaaaace3cea0,0xaaaaace3cee0),  
          5: INFO: -max_len is not provided; libFuzzer will not generate inputs larger than 4096 bytes 
          6: INFO: A corpus is not provided, starting from an empty corpus 
          7: INFO: signal received, trying to exit gracefully 
check:17                                                     X error: no match found
>>>>>>

--

...

```

</details>

https://github.com/llvm/llvm-project/pull/107931