List of non-vanilla compiletest-like directives to support

[fmease]

• Support for "non-standard" directive syntax: Inline crates #26
• Support for "non-standard" directive syntax: "Cfg specs" in revision "attributes" #25
• (maybe) some way/mechanism to avoid the need of an auxiliary/ directory (annoying for local hacking) by e.g.
  • resolving paths in aux-* directives lexically (cc [#]134694) via an extra CLI flag or by default (-@@) so you can simply write ../file.rs which would expand to $CWD/auxiliary/../file.rs and resolve to $CDW/file.rs thus absolving the user of having to create an empty "dummy" auxiliary/ or by
  • adding a new set of directives (ideally via a simple marker like a suffix) which don't add the path component auxiliary or by
  • adding a flag that changes the behavior of existing aux-* directives to not look into auxiliary/ (hmm)
• (maybe) introduce a new form for aux-bin: aux-bin:ENV_VAR=PATH which is like aux-bin:PATH except that it adds env var ENV_VAR to the rustc invocation which contains the path to the built aux bin
  • simply for convenience; the crate no longer need to manually deal with EXE_EXTENSION etc
  • the value of the env var will have the shape auxiliary/bin/PATH_WITH_EXE_EXTENSION
• (maybe) allow the path to be omitted in aux-crate: aux-crate:name would expand to aux-crate=name=name.rs