CMakeParseImplicitLinkInfo: Honor GNU static runtime library flags

Brad Kingrequested to merge
brad.king/cmake:implicit-link-static into master

With flags like -static-libstdc++ or -static-libgfortran, the GNU compiler driver adds -Bstatic ... -Bdynamic around its language runtime library. Convert the libraries in between these to absolute paths so that mixed-language linking honors the static runtime libraries.

Edited by Brad King

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