make: Fix tests.
make: Fix tests.

Some of the tests that chdir around complain that the `mkdir` call for the temporary directory fails. As a workaround, use the system TMPDIR instead, which always exists already.

(I noticed go/gypbot doesn't run tests for the make generator on mac. That's being fixed now.)
Review URL: http://codereview.chromium.org/7530006
old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google