Log Message:
MesaLib: fix PR 54823

pkgsrc changes:
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  * Undefine ALIGN symbol as close as possible to the ALIGN function since
    it is defined in machine/param.h on FreeBSD.
  * Add test to verify there is at least one needed gallium driver for VA.
    On FreeBSD, nouveau is disabled and r600 and radeonsi are enabled only
    if llvm option is activated.