Unit tests on Windows are supposed to pass for any PR to pass CI.
However, the return code for the unit test command was not being
checked, which meant this check was always passing (effectively
disabled). This PR
* Properly checks the result of the unit tests and fails if the
unit tests fail
* Fixes (or disables on Windows) a number of tests which have
"drifted" out of support on Windows since this check was
effectively disabled
This PR introduces a new build cache layout and package format, with improvements for
both efficiency and security.
## Old Format
Currently a binary package consists of a `spec.json` file at the root and a `.spack` file,
which is a `tar` archive containing a copy of the `spec.json` format, possibly a detached
signature (`.asc`) file, and a tar-gzip compressed archive containing the install tree.
```
build_cache/
# metadata (for indexing)
<arch>-<compiler>-<name>-<ver>-24zvipcqgg2wyjpvdq2ajy5jnm564hen.spec.json
<arch>/
<compiler>/
<name>-<ver>/
# tar archive
<arch>-<compiler>-<name>-<ver>-24zvipcqgg2wyjpvdq2ajy5jnm564hen.spack
# tar archive contents:
# metadata (contains sha256 of internal .tar.gz)
<arch>-<compiler>-<name>-<ver>-24zvipcqgg2wyjpvdq2ajy5jnm564hen.spec.json
# signature
<arch>-<compiler>-<name>-<ver>-24zvipcqgg2wyjpvdq2ajy5jnm564hen.spec.json.asc
# tar.gz-compressed prefix
<arch>-<compiler>-<name>-<ver>-24zvipcqgg2wyjpvdq2ajy5jnm564hen.tar.gz
```
After this change, the nesting has been removed so that the `.spack` file is the
compressed archive of the install tree. Now signed binary packages, will take the
form of a clearsigned `spec.json` file (a `spec.json.sig`) at the root, while unsigned
binary packages will contain a `spec.json` at the root.
## New Format
```
build_cache/
# metadata (for indexing, contains sha256 of .spack file)
<arch>-<compiler>-<name>-<ver>-24zvipcqgg2wyjpvdq2ajy5jnm564hen.spec.json
# clearsigned spec.json metadata
<arch>-<compiler>-<name>-<ver>-24zvipcqgg2wyjpvdq2ajy5jnm564hen.spec.json.sig
<arch>/
<compiler>/
<name>-<ver>/
# tar.gz-compressed prefix (may support more compression formats later)
<arch>-<compiler>-<name>-<ver>-24zvipcqgg2wyjpvdq2ajy5jnm564hen.spack
```
## Benefits
The major benefit of this change is that the signatures on binary packages can be
verified without:
1. Having to download the tarball, or
2. having to extract an unknown tarball.
(1) is an improvement in efficiency; (2) is a security fix: we now ensure that we trust the
binary before we try to run it through `tar`, which avoids potential attacks.
## Backward compatibility
Also after this change, spack should still be able to handle the previous buildcache
structure and binary mirrors with mixed layouts.
