[llvm-lit] Environment variable not found in LLVM subproject with lit internal shell

[Harini0924]

Currently, an environment variable is not recognized within the LLVM subproject, resulting in test failures when using the lit internal shell.
Error displayed:

'JITDUMPDIR=/usr/local/google/home/harinidonthula/llvm-project/build/test/ExecutionEngine/JITLink/x86-64/Output/ELF_perf.s.tmp': command not found

This error indicates that the internal shell is misinterpreting environment variable assignments as commands, leading to these failures.