ci,README: improve install instructions

.github/workflows/go.yml

@@ -32,10 +32,10 @@ jobs:
       - name: Install LLVM ${{ matrix.llvm }} and libgc-dev
         if: startsWith(matrix.os, 'ubuntu')
         run: |
-          echo 'deb http://apt.llvm.org/focal/ llvm-toolchain-focal-${{ matrix.llvm }} main' | sudo tee /etc/apt/sources.list.d/llvm.list
+          echo "deb http://apt.llvm.org/$(lsb_release -cs)/ llvm-toolchain-$(lsb_release -cs)-${{ matrix.llvm }} main" | sudo tee /etc/apt/sources.list.d/llvm.list
           wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
           sudo apt-get update
-          sudo apt-get install --no-install-recommends clang-${{ matrix.llvm }} llvm-${{ matrix.llvm }}-dev libgc-dev
+          sudo apt-get install -y --no-install-recommends llvm-${{ matrix.llvm }}-dev clang-${{ matrix.llvm }} lld-${{ matrix.llvm }} libgc-dev
           echo /usr/lib/llvm-${{ matrix.llvm }}/bin >> $GITHUB_PATH
     
       - name: Clang information

README.md

@@ -219,19 +219,19 @@ Follow these steps to generate the `llgo` command (its usage is the same as the
 
 ```sh
 brew update # execute if needed
-brew install libgc
-brew install llvm@17
+brew install llvm@17 libgc
+export PATH=$(brew --prefix llvm@17)/bin:$PATH # you may want to add this to your shell RC file, e.g. ~/.zshrc
 go install -v ./...
 ```
 
-### on Linux
+### on Linux (Debian/Ubuntu)
 
 ```sh
-echo 'deb http://apt.llvm.org/focal/ llvm-toolchain-focal-17 main' | sudo tee /etc/apt/sources.list.d/llvm.list
+echo "deb http://apt.llvm.org/$(lsb_release -cs)/ llvm-toolchain-$(lsb_release -cs)-17 main" | sudo tee /etc/apt/sources.list.d/llvm.list
 wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
 sudo apt-get update # execute if needed
-sudo apt-get install libgc-dev
-sudo apt-get install --no-install-recommends llvm-17-dev
+sudo apt-get install -y --no-install-recommends llvm-17-dev clang-17 lld-17 libgc-dev
+export PATH=/usr/lib/llvm-17/bin:$PATH # you may want to add this to your shell RC file, e.g. ~/.bashrc
 go install -v ./...
 ```