download-toolchain: pull v17 cheriot llvm from proper location

The v17-based llvm toolchain is now in the master repo; grab it from there.

Bypass-Presubmit-Reason: no presubmit tests; manually tested

Change-Id: Iaed16dce019433907cab5d338516bc098d974f10

download-toolchain.sh

diff --git a/download-toolchain.sh b/download-toolchain.sh
index 4ad48fa..26e5b8e 100755
--- a/download-toolchain.sh
+++ b/download-toolchain.sh
@@ -40,10 +40,8 @@
 TOOLCHAIN_GCC_URL="https://github.com/riscv/riscv-gnu-toolchain"
 TOOLCHAINLLVM_BINUTILS_URL="git://sourceware.org/git/binutils-gdb.git"
 
-#TOOLCHAIN_CHERIOT_TAG=
-#TOOLCHAIN_CHERIOT_URL="https://github.com/CHERIoT-Platform/llvm-project"
-TOOLCHAIN_CHERIOT_URL="https://github.com/sleffler/llvm-project"
-TOOLCHAIN_CHERIOT_TAG="cheriot-merge-cleanup-1"
+TOOLCHAIN_CHERIOT_TAG=cheriot
+TOOLCHAIN_CHERIOT_URL="https://github.com/CHERIoT-Platform/llvm-project"
 TOOLCHAIN_CHERIOT_SRC="${TOOLCHAIN_SRC}/cheriot-llvm-project"
 
 if [[ ! "${TOOLCHAIN_TARGET}" == "GCC" ]] &&