Check for `.exe` case insensitively
Check for `.exe` case insensitively

On Windows `foo.exe`, `foo.eXe` and `foo.EXE` are equally executable.

Signed-off-by: Ian Campbell <a8db091655a7f47ecb9c39a2d278e9662e440dc0@docker.com>

thaJeztah/cli,docker/cli,cpuguy83/cli,thaJeztah/cli,docker/cli,cpuguy83/cli