Revert r227403 for now.  Since the cross-tools stage purposefully doesn't have ${WORLDTMP}/usr/bin in its PATH, if you build world with CC=clang, tblgen tools from /usr/bin will be used instead of the ones built under ${WORLDTMP}.  This can lead to various errors, especially if you upgrade from an older clang.
Revert r227403 for now.  Since the cross-tools stage purposefully
doesn't have ${WORLDTMP}/usr/bin in its PATH, if you build world with
CC=clang, tblgen tools from /usr/bin will be used instead of the ones
built under ${WORLDTMP}.  This can lead to various errors, especially if
you upgrade from an older clang.

Note that building world with gcc would not experience these problems,
because it only uses the tblgen tools in the world stage, where PATH
does contain ${WORLDTMP}/usr/bin.

Pointy hat to:	dim

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