As of #18205, all packages must be pickle-able to be installed by
Spack.

This adds a test to check that each package can be pickled. If any
package fails to pickle, the test keeps going and collects the names
of all failed packages; it then takes the first one that failed and
attempts to re-pickle it, generating the full stack trace for the
failed pickle attempt.

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.

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 spack#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.

This object was introduced in spack#18124 which
was later superseded by spack#18205 and removed
any use if the object.

This object was introduced in #18124, and was later superseded by
#18205 and removed any use if the object.