Fix CI flakiness

[martincostello]

Despite some previous attempts (see #2836), there's still some instability in CI, such as #2886.

We need to come up with good lasting solution to avoid these write conflicts in build and test.

[martincostello]

When resolved, un-skip this test:

Swashbuckle.AspNetCore/test/Swashbuckle.AspNetCore.Cli.Test/ToolTests.cs

Lines 31 to 32 in d793865

	[Fact(Skip = "Disabled because it makes CI unstable")]
	public void Overwrites_Existing_File()