test/run.go: fix compiledir test on windows     we can't import "./bug0" on windows, as it will trigger "import path contains invalid character ':'" error.     instead, we pass "-D." and "-I." to gc to override this behavior. this idea is due to remyoudompheng.
test/run.go: fix compiledir test on windows
    we can't import "./bug0" on windows, as it will trigger
"import path contains invalid character ':'" error.
    instead, we pass "-D." and "-I." to gc to override this
behavior. this idea is due to remyoudompheng.

R=golang-dev, r, alex.brainman, remyoudompheng
CC=golang-dev
http://codereview.appspot.com/6441074

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