Debugging support: fix compiler wrapper log on Mac OS (#20333)

This fixes a logging error observed on macOS 11.0.1 (Big Sur).
When performing a Spack install in debugging mode (e.g.
`spack -d install py-scipy`) Spack is supposed to write a log of
compiler wrapper command line invocations to the current working
directory.

Due to a regression error introduced by #18205, these files were
no-longer generated, and Spack was printing errors such as
"No such file or directory: None/." This is because the log file
directory gets set from `spack.main.spack_working_dir`, but that
variable is not set in the spawned process.

This PR ensures that the working directory (at the time of the
"spack install" invocation) is persisted to the subprocess.

0 files changed, 0 insertions, 0 deletions