add 'nmake' to list of make variants probed during config. this change allows msvc6 to run makefiles successfully.
add 'nmake' to list of make variants probed during config.
this change allows msvc6 to run makefiles successfully.

git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@10118 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

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