Do not use the powershell step

[mattleibow]

Description of Change

Alternative to #19257

This is to address a reliability issue involving MAUI-DeviceTests. Tests run on Mac sporadically hang then fail (timeout) due to the following error:

The STDIO streams did not close within 10 seconds of the exit event from process '/usr/local/bin/pwsh'. This may indicate a child process inherited the STDIO streams and has not yet exited.

It seems that build.ps1 is getting executed as a powershell subprocess and in turn interfering with the IO stream for the pwsh step. As a mitigation, run build.ps1 under a bash step on Mac. This avoids flakiness and in turn avoids having to rerun failed tests.

[mjbond-msft]

@mattleibow - I see the Windows device tests failed, which is a challenge I also faced. Perhaps they need to be run under powershell and not pwsh? but, on Mac definitely need to be run under pwsh

[rmarinho]

Closing this one for now