install_prereq() {
curl https://apt.llvm.org/llvm-snapshot.gpg.key|apt-key add -
- add-apt-repository -y 'deb http://apt.llvm.org/focal/ llvm-toolchain-focal-11 main'
+ add-apt-repository -y 'deb https://apt.llvm.org/focal/ llvm-toolchain-focal-11 main'
apt-get update
apt-get install -y --no-install-recommends \
build-essential \