Fix duplicate -I's harmless under gcc but which break bunny-gcc

(This helps us do some instrumented fuzz testing with "bunny the fuzzer".)

Change-Id: I4d06129d577115b9dd5cd9bec2c2e1b526490456

BUG=chromium-os:13690
TEST="CC=/usr/local/google/bunny-0.93/bunny-gcc make -k" now builds vbutil_*, and regular gcc/make did not break.
STATUS=Fixed

Review URL: http://codereview.chromium.org/6783006
1 file changed