"@" in path broke "copy always" option for files in .net9 sdk

[HerrTete]

Describe the bug

Since .net9 files with "Always" are no longer copied to the outputfolder if the path of the projectfolder or any folder above it contains a "@". We found this behavior on our jenkins, because he creates for each worker a folder containing a "@".

To Reproduce

1. Create a folder like "test@dotnet"
2. Create a new dotnet console application
3. add a file with "copy always"
4. build
5. => the file isnt copied

workarounds
option 1
create a global.json force to dotnet 8 sdk and retry
option 2
remove the "@" from the foldername

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[allenh9999]

I also have an issue where the files that are set to copy always and don't copy over have a set of parenthesis, like (1).
Perhaps these 2 issues are related?

[edvilme]

Looks similar to #46833 (i.e., related to characters being escaped incorrectly and not being able to find the location), although I think this is an MSBuild issue?