run-vmtest: set default LLVM_VERSION to 21

Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>

Author: theihor

run-vmtest/install-dependencies.sh

@@ -2,6 +2,7 @@
 
 set -euo pipefail
 
+LLVM_VERSION=${LLVM_VERSION:-21}
 VMTEST_RELEASE=${VMTEST_RELEASE:-v0.18.0}
 VMTEST_URL="https://github.com/danobi/vmtest/releases/download/${VMTEST_RELEASE}/vmtest-$(uname -m)"
 sudo curl -L $VMTEST_URL -o /usr/bin/vmtest