Fixes#11781
* Rename build log to spack-build-log.txt
* Rename environment variables file to spack-build-env.txt
* The name of the log and env files is now the same during the build
and after the build completes
* Update packages which referred to the build log/env files
* For packages installed before this commit using older names for the
build and env files, search for the older names
e3299e6923