Try to use HOME environment value first on Windows.

On Windows + MinGW/MSYS envrionment,
it seems base system of MSYS rewrites HOMEPATH environment value.
For example, `\Users\koron` -> `\` on my environment.
Therefore, HOMEDRIVE + HOMEPATH is evaluated as `C:\` and be used as home directory,
where normal users don't have any rights to write.

I have created this evasive change, and I know it is not good solution.
But I don't have any better idea for now.