Only remove newly installed llvm packages and not always everything

features/src/llvm/install.sh

@@ -41,7 +41,14 @@ echo "Installing llvm-${LLVM_VERSION} compilers and tools";
 ./llvm.sh $LLVM_VERSION ${PACKAGES:-all};
 
 # Remove existing, install, and set default clang/llvm alternatives
-for x in clang clangd clang++ clang-format clang-tidy lldb llvm-config llvm-cov; do
+if [[ -z "$PACKAGES" \
+      || "$PACKAGES" == "all"
+]]; then
+    INSTALLED_PACKAGES = (clang clangd clang++ clang-format clang-tidy lldb llvm-config llvm-cov);
+else
+    INSTALLED_PACKAGES = "${PACKAGES}";
+fi
+for x in ${INSTALLED_PACKAGES[@]} do
     if type ${x}-${LLVM_VERSION} >/dev/null 2>&1; then
         (update-alternatives --remove-all ${x} >/dev/null 2>&1 || true);
         (update-alternatives --install /usr/bin/${x} ${x} $(which ${x}-${LLVM_VERSION}) 30);