[llvm] [lit] Fix to make "RUN: env PATH=..." work as intended (PR #165308)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-4` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/29879

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll' FAILED ********************
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 1
/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli -jit-kind=orc-lazy -compile-threads=2 -thread-entry hello /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll | /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll
# executed command: /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli -jit-kind=orc-lazy -compile-threads=2 -thread-entry hello /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll
# .---command stderr------------
# | PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
# | Stack dump:
# | 0.	Program arguments: /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli -jit-kind=orc-lazy -compile-threads=2 -thread-entry hello /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll
# |  #0 0x0000000101804768 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100f30768)
# |  #1 0x0000000101802518 llvm::sys::RunSignalHandlers() (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100f2e518)
# |  #2 0x0000000101805268 SignalHandler(int, __siginfo*, void*) (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100f31268)
# |  #3 0x000000019bd2f584 (/usr/lib/system/libsystem_platform.dylib+0x18047b584)
# |  #4 0x00000101013590d8
# |  #5 0x0000000101362e34 llvm::orc::ExecutionSession::removeJITDylibs(std::__1::vector<llvm::IntrusiveRefCntPtr<llvm::orc::JITDylib>, std::__1::allocator<llvm::IntrusiveRefCntPtr<llvm::orc::JITDylib>>>) (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100a8ee34)
# |  #6 0x0000000101362be4 llvm::orc::ExecutionSession::endSession() (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100a8ebe4)
# |  #7 0x00000001013ef85c llvm::orc::LLJIT::~LLJIT() (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100b1b85c)
# |  #8 0x00000001013f41e8 llvm::orc::LLLazyJIT::~LLLazyJIT() (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100b201e8)
# |  #9 0x00000001008dca2c runOrcJIT(char const*) (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100008a2c)
# | #10 0x00000001008d7f18 main (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100003f18)
# | #11 0x000000019b973154
# `-----------------------------
# error: command failed with exit status: -11
# executed command: /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll
# .---command stderr------------
# | FileCheck error: '<stdin>' is empty.
# | FileCheck command line:  /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll
# `-----------------------------
# error: command failed with exit status: 2

--

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


```

</details>

https://github.com/llvm/llvm-project/pull/165308