Yet another MSBuild-on-Linux back-slash gotcha

Another variant of a known family of such issues, encountered as AltCover issue #49, the interesting tale of what you get when your MSBuild sets a task array parameter with

AssemblyExcludeFilter="$(AltCoverAssemblyExcludeFilter.Split('|'))"

and the value of AltCoverAssemblyExcludeFilter is the-|xunit\.; surprisingly, the answer is

the-
xunit/.

There isn't even an explicit ItemList in sight, and yet the '\' still gets interpreted as a path separator and "helpfully" *nix-ified. Doubling up the '\' via .Replace('\','\\') ahead of the split doesn't escape the character -- you just get a '//' in the output, nor does escaping on the command line as the-|xunit%5C..

For the moment, with no obvious MSBuild level fix, I'm working around this by doing .Replace('\', %00) and then converting the NUL back inside the custom MSBuild task.