Optimize setting LLVM version for TLCPack (#191)

This change fixes issue apache/tvm#16613

Changes the script `centos_build_llvm.sh` to discover what tags are
available in the LLVM project using `git ls-remote`. This is a more
efficient approach, as it doesn't use the Github API and therefore isn't
impacted by API rate limits, which will prevent the script from working
correctly. The end result is the same and retrieves the latest semantic
version for LLVM in the format XX.X.XX, e.g. 16.0.6.

docker/install/centos_build_llvm.sh

@@ -7,12 +7,10 @@ LLVM_VERSION_MAJOR=$1
 source /multibuild/manylinux_utils.sh
 
 detect_llvm_version() {
-  curl -sL "https://api.github.com/repos/llvm/llvm-project/releases?per_page=100" | \
-    grep tag_name | \
-    grep -o "llvmorg-${LLVM_VERSION_MAJOR}[^\"]*" | \
-    grep -v rc | \
-    sed -e "s/^llvmorg-//g" | \
-    head -n 1
+  git ls-remote --sort='v:refname' --tags --refs 'https://github.com/llvm/llvm-project' | \
+     grep "llvmorg-${LLVM_VERSION_MAJOR}" | \
+     grep -v 'rc' | \
+     awk 'BEGIN { FS="-" } END {print $2}'
 }
 
 LLVM_VERSION=$(detect_llvm_version)