bevy run web: only compile default_run target when no binary is specified

[DaAlbrecht]

Objective

Closes #200.

Improve compile time by only compiling the default run target if available and no specific binary is omitted via the --bin or --example flags.

Solution

Check if bevy run was called with either --bin or --example. If not search for the default_run binary name and append it with --bin before calling build_web(&mut build_args)

Testing

Before:

bevy_complex_repo/app
❯ cargo clean
     Removed 2378 files, 2.6GiB total
bevy_complex_repo/app
❯ bevy run web
Compiling to WebAssembly...
   Compiling cplx_core v0.1.0 
   Compiling cplx_teaser v0.1.0
   Compiling cplx v0.1.0 
   Compiling cplx_demo v0.1.0 
    Finished `web` profile [unoptimized + debuginfo] target(s) in 37.09s
Bundling JavaScript bindings...

Now:

bevy_complex_repo/app
❯ cargo clean
     Removed 2724 files, 6.9GiB total
bevy_complex_repo/app
❯ bevy run web
 Compiling bevy v0.14.2
   Compiling cplx v0.1.0 
    Finished `web` profile [unoptimized + debuginfo] target(s) in 39.44s

[TimJentzsch]

I first though this might not work if you have two different packages which contain a binary with the same name.

But it turns out Cargo doesn't allow that in workspaces, at least it prints out a warning in this case.