[SDK tools] Support non-ASCII paths in 'mksdcard'

Use platform-specific code to support extended character
sets on Windows, Mac and Linux.

Fixes: 72193737

Test: Manually verified with path 'Юзер' on Windows, Mac, Linux

Change-Id: Ib37d95b0f1c9fe1961b1a742cece362fdfcbd58a
1 file changed