Change in coreboot[master]: Fix build with CLANG, avoid GCC only CFLAGS

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build bot (Jenkins) has posted comments on this change. ( https://review.coreboot.org/21202 )

Change subject: Fix build with CLANG, avoid GCC only CFLAGS
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Patch Set 1: Verified+1

Build Successful

https://qa.coreboot.org/job/coreboot-checkpatch/14633/ : SUCCESS

https://qa.coreboot.org/job/coreboot-gerrit/59307/ : SUCCESS