Compile libraries and binaries at workspace level if building workspace

[azriel91]

When compiling libraries and binaries for a workspace, if member crates are compiled individually, then crates that are common dependencies may be compiled multiple times¹.

In addition, cargo build --all performs compilation on multiple threads, so the wall clock time is shorter.

$ time (for crate in $(ls crate); do; ( cd crate/$crate; cargo test --release;)
# ... elided
1652.02s user 51.42s system 303% cpu 9:21.12 total

$ time cargo test --all --release
# ... elided
1680.56s user 55.82s system 482% cpu 5:59.60 total

We should change the build command entry to build at the workspace level when building a workspace.

¹ I've seen this on Windows. On Ubuntu the common dependencies are only compiled once.

[azriel91]

Just discovered cargo build --all-targets, which does what I wanted with hull build (and more).

cargo build --all-targets builds lib and bin targets at debug and optimized levels. What we want is lib, bin, and example targets at just debug or just release levels (based on active profile).

cargo build --examples builds all examples in the workspace if invoked at workspace level. Perhaps just using bare cargo commands is good enough.

[azriel91]

The current mechanism of hull each -- <command> doesn't work on Windows, as it tacks on the members to the canonicalized workspace path, e.g. \\?\D:\path\to\workspace\app/*\Cargo.toml, which fails to resolve on Windows. The app/* comes from the workspace's member dependencies.