Standard golang's `os.MkdirAll()` function returns "not a directory" error
in case a directory to be created already exists but is not a directory
(e.g. a file). Our own `idtools.MkdirAs*()` functions do not replicate
the behavior.
This is a bug since all `Mkdir()`-like functions are expected to ensure
the required directory exists and is indeed a directory, and return an
error otherwise.
As the code is using our in-house `system.Stat()` call returning a type
which is incompatible with that of golang's `os.Stat()`, I had to amend
the `system` package with `IsDir()`.
A test case is also provided.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Upstream-commit: 2aa13f86f0c9cf3ed58a648a7b1506d4b06f3589
Component: engine
03d850d672