Paths resolving to c:\ or c:\windows are forbidden
Replaced the obscure (and non-working) regex with a simple case
insensitive comparison to the black listed paths (we should forbid c:\,
c:\windows but not d:\)
Also, add a test ensuring paths are case insensitive on windows
Also, made sure existing multi-staged build tests pass on windows
Signed-off-by: Simon Ferquel <simon.ferquel@docker.com>
Upstream-commit: b0e75888738f6e427b545922a195837c00158749
Component: engine