The LLVM's main branch prohibits standalone build for a while. However,
LLVM doesn't support bootstrap crt builds. The patch to solve this problem
is https://reviews.llvm.org/D89492, but it is not merged yet.
So, compiling LLVM for VE used to require several tricks. Recently, a
patch at https://reviews.llvm.org/D137024 breaks such tricks. As a
result, VE's buildbot was not possible to perform tests, particulaly a
check-compiler-rt for VE. This patch udpate buildbot script to perform
tests again on VE's buildbot.