Update build_deps.yml (add missing '-p' for mkdir)

[tsmith35]

Fixes "Build on Windows" so an error isn't thrown if the working directories already exist. I simply added "-p" to the mkdir commands.

Screenshots/Recordings/Graphs

Before the change:

Will need testing, but it is a simple change to bring "Build on Windows" in line with the other OS builds.

[tsmith35]

@SoftFever this PR is very simple. Just added '-p' to a couple of mkdir commands for building Windows deps.

[tsmith35]

@Noisyfox ... do these changes appear to be correct? Without the "-p", the simple act of making the build directory results in an error if the directory already exists, thereby preventing the deps from being built.

[Noisyfox]

I don't think -p works on windows.

[tsmith35]

I don't think -p works on windows.

From what I've seen, the YAML files on Github appear to be processed with Linux. There are four other "mkdir -p" instances in the original file, so I just copied that. I tried building the deps numerous times without success, but adding the "-p" did the trick.

I Googled for >> "An item with the specified name" "already exists." << and found that it is specific to PowerShell. So that's interesting. But PowerShell doesn't support "-p" for mkdir.

[Noisyfox]

See
https://github.blog/changelog/2019-10-17-github-actions-default-shell-on-windows-runners-is-changing-to-powershell/
and
https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsshell

[tsmith35]

@Noisyfox I think I figured out why adding the "-p" fixed the issue; the argument is invalid in PS, so it didn't attempt to create the directory. I'll correct it a different way and update the PR. Thanks for your help!