[llvm] [JITLink][LoongArch] Add R_LARCH_{B16, B21} relocations support (PR #121096)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lldb-x86_64-debian` running on `lldb-x86_64-debian` while building `llvm` at step 6 "test".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/162/builds/13311

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

```
Step 6 (test) failure: build (failure)
...
PASS: lldb-api :: lang/rust/enum-structs/TestRustEnumStructs.py (141 of 2735)
PASS: lldb-api :: functionalities/breakpoint/scripted_bkpt/TestScriptedResolver.py (142 of 2735)
PASS: lldb-api :: functionalities/thread/step_out/TestThreadStepOut.py (143 of 2735)
PASS: lldb-api :: lang/cpp/union-static-data-members/TestCppUnionStaticMembers.py (144 of 2735)
PASS: lldb-api :: tools/lldb-dap/commands/TestDAP_commands.py (145 of 2735)
PASS: lldb-api :: python_api/frame/TestFrames.py (146 of 2735)
PASS: lldb-shell :: Subprocess/clone-follow-child-wp.test (147 of 2735)
PASS: lldb-api :: commands/process/launch/TestProcessLaunch.py (148 of 2735)
PASS: lldb-api :: functionalities/single-thread-step/TestSingleThreadStepTimeout.py (149 of 2735)
PASS: lldb-api :: lang/cpp/virtual-functions/TestCppVirtualFunctions.py (150 of 2735)
FAIL: lldb-api :: functionalities/thread/thread_specific_break_plus_condition/TestThreadSpecificBpPlusCondition.py (151 of 2735)
******************** TEST 'lldb-api :: functionalities/thread/thread_specific_break_plus_condition/TestThreadSpecificBpPlusCondition.py' FAILED ********************
Script:
--
/usr/bin/python3 /home/worker/2.0.1/lldb-x86_64-debian/llvm-project/lldb/test/API/dotest.py -u CXXFLAGS -u CFLAGS --env LLVM_LIBS_DIR=/home/worker/2.0.1/lldb-x86_64-debian/build/./lib --env LLVM_INCLUDE_DIR=/home/worker/2.0.1/lldb-x86_64-debian/build/include --env LLVM_TOOLS_DIR=/home/worker/2.0.1/lldb-x86_64-debian/build/./bin --arch x86_64 --build-dir /home/worker/2.0.1/lldb-x86_64-debian/build/lldb-test-build.noindex --lldb-module-cache-dir /home/worker/2.0.1/lldb-x86_64-debian/build/lldb-test-build.noindex/module-cache-lldb/lldb-api --clang-module-cache-dir /home/worker/2.0.1/lldb-x86_64-debian/build/lldb-test-build.noindex/module-cache-clang/lldb-api --executable /home/worker/2.0.1/lldb-x86_64-debian/build/./bin/lldb --compiler /home/worker/2.0.1/lldb-x86_64-debian/build/./bin/clang --dsymutil /home/worker/2.0.1/lldb-x86_64-debian/build/./bin/dsymutil --make /usr/bin/gmake --llvm-tools-dir /home/worker/2.0.1/lldb-x86_64-debian/build/./bin --lldb-obj-root /home/worker/2.0.1/lldb-x86_64-debian/build/tools/lldb --lldb-libs-dir /home/worker/2.0.1/lldb-x86_64-debian/build/./lib -t /home/worker/2.0.1/lldb-x86_64-debian/llvm-project/lldb/test/API/functionalities/thread/thread_specific_break_plus_condition -p TestThreadSpecificBpPlusCondition.py
--
Exit Code: 1

Command Output (stdout):
--
lldb version 20.0.0git (https://github.com/llvm/llvm-project.git revision 4c5c5e2f41e62e4be9ca7bb6c42221cc11700321)
  clang revision 4c5c5e2f41e62e4be9ca7bb6c42221cc11700321
  llvm revision 4c5c5e2f41e62e4be9ca7bb6c42221cc11700321
Skipping the following test categories: ['libc++', 'dsym', 'gmodules', 'debugserver', 'objc']

--
Command Output (stderr):
--
Change dir to: /home/worker/2.0.1/lldb-x86_64-debian/llvm-project/lldb/test/API/functionalities/thread/thread_specific_break_plus_condition
UNSUPPORTED: LLDB (/home/worker/2.0.1/lldb-x86_64-debian/build/bin/clang-x86_64) :: test_python_dsym (TestThreadSpecificBpPlusCondition.ThreadSpecificBreakPlusConditionTestCase.test_python_dsym) (test case does not fall in any category of interest for this run) 
runCmd: settings clear -all

output: 

runCmd: settings set symbols.enable-external-lookup false

output: 

runCmd: settings set target.inherit-tcc true

output: 

runCmd: settings set target.disable-aslr false

output: 

runCmd: settings set target.detach-on-error false

output: 

```

</details>

https://github.com/llvm/llvm-project/pull/121096