Change in coreboot[master]: crossgcc: Fix building with clang++ in the presence of gcc

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Change subject: crossgcc: Fix building with clang++ in the presence of gcc
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Patch Set 1: Verified+1

Build Successful

https://qa.coreboot.org/job/coreboot-gerrit/56190/ : SUCCESS

https://qa.coreboot.org/job/coreboot-checkpatch/11792/ : SUCCESS

https://qa.coreboot.org/job/coreboot-toolchain/313/ : SUCCESS