Fix typo to make clang plugin tests work on linux.
Fix typo to make clang plugin tests work on linux.

(Happened to work on OS X due to it having a case-insensitive
file system.)

BUG=none
TEST=tools/clang/scripts/package.sh successfully runs tests on linux.
TBR=erg

Review URL: http://codereview.chromium.org/8370018

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@106845 0039d316-1c4b-4281-b951-d872f2087c98

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