Avoid warning on "clang -c -Dfoo test.i". Lines like these are created when using ccache and libtool.m4 assumes that the compiler cannot print warnings about options it knows about.
Avoid warning on "clang -c -Dfoo test.i". Lines like these are created
when using ccache and libtool.m4 assumes that the compiler cannot print
warnings about options it knows about.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@135723 91177308-0d34-0410-b5e6-96231b3b80d8

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