dockcross: Add support for Windows

Tested on Git Bash and Bash on Ubuntu for Windows.

There are some issue with building the Docker image itself, but using the
images works great.

imagefiles/dockcross

@@ -171,18 +171,35 @@ fi
 # Set the docker run extra args (if any)
 FINAL_ARGS=${ARG_ARGS-${DOCKCROSS_ARGS}}
 
-# If we are not running via boot2docker
-if [ -z $DOCKER_HOST ]; then
+# Bash on Ubuntu on Windows
+UBUNTU_ON_WINDOWS=$(grep -l Microsoft /proc/version)
+# MSYS, Git Bash, etc.
+MSYS=$(grep -l MINGW /proc/version)
+
+if [ -z "$UBUNTU_ON_WINDOWS" -a -z "$MSYS" ]; then
     USER_IDS="-e BUILDER_UID=$( id -u ) -e BUILDER_GID=$( id -g ) -e BUILDER_USER=$( id -un ) -e BUILDER_GROUP=$( id -gn )"
 fi
 
+# Change the PWD when working in Docker on Windows
+if [ -n "$UBUNTU_ON_WINDOWS" ]; then
+    HOST_PWD=$PWD
+    HOST_PWD=${HOST_PWD/\/mnt\//}
+    HOST_PWD=${HOST_PWD/\//:\/}
+elif [ -n "$MSYS" ]; then
+    HOST_PWD=$PWD
+    HOST_PWD=${HOST_PWD/\//}
+    HOST_PWD=${HOST_PWD/\//:\/}
+else
+    HOST_PWD=$PWD
+fi
+
 #------------------------------------------------------------------------------
 # Now, finally, run the command in a container
 #
 tty -s && TTY_ARGS=-ti || TTY_ARGS=
 CONTAINER_NAME=dockcross_$RANDOM
 docker run $TTY_ARGS --name $CONTAINER_NAME \
-    -v $PWD:/work \
+    -v $HOST_PWD:/work \
     $USER_IDS \
     $FINAL_ARGS \
     $FINAL_IMAGE "$@"