Revert "[RT #54703] Don't hardcode /cygdrive"

This has been found to cause more problems that it solves.

There is a patch from Reini that pertains to resolve the same issue.

This reverts commit 22dd67bcc830fe30ab915b2ab1ef8362bbef8203.
[RT #69401] 93862c2 Stabilize ExtUtils::MM_Cygwin::maybe_command

also [perl #94532]

Be independent of /cygdrive prefixes. Failed with a prefix like "/".
Suggestion by Marco Moreno, patch by Reini Urban.

Also resolves [RT #54703] [PATCH] Don't hardcode /cygdrive

Signed-off-by: Chris 'BinGOs' Williams <chris@bingosnet.co.uk>