While reviewing our MSBuild targets, I noticed three targets that
declared `Inputs` and `Outputs`, but did not actually update any
files:
- `_CollectConfigFiles`
- `_CollectMdbFiles`
- `_CollectPdbFiles`
This means that MSBuild was unnecessarily looking at files to see if
they exist, and might be comparing timestamps as well. The targets
would also _always_ run, so it doesn't matter to have `Inputs` and
`Outputs` in these targets at all!
I basically removed these `Inputs` and `Outputs`, and saw a
performance gain with just doing that. I also saw performance gains to
targets that depend on these three targets. Since `Inputs` and
`Outputs` timing is internal to MSBuild, I am not sure where the
actual time is being tallied here.
    Before:
        1 ms  _CopyConfigFiles                           1 calls
        3 ms  _CopyMdbFiles                              2 calls
        3 ms  _CollectMdbFiles                           1 calls
        4 ms  _CopyPdbFiles                              1 calls
        5 ms  _CollectPdbFiles                           1 calls
        5 ms  _CollectConfigFiles                        1 calls
       20 ms  _ConvertPdbFiles                           1 calls
A total of ~46ms
    After:
        0 ms  _ConvertPdbFiles                           1 calls
        0 ms  _CopyPdbFiles                              1 calls
        1 ms  _CollectMdbFiles                           1 calls
        1 ms  _CopyMdbFiles                              2 calls
        1 ms  _CopyConfigFiles                           1 calls
        2 ms  _CollectConfigFiles                        1 calls
        5 ms  _CollectPdbFiles                           1 calls
A total of ~10ms
An overall improvement of ~36ms.
This was the `samples/HelloWorld` project in this repo, a build with
no changes. I suspect the improvement would be even better for larger
projects.