scripts(setup-ubuntu.sh): Add [arch=amd64] to the llvm repo

Avoids a warning on `apt update`:

> N: Skipping acquire of configured file 'main/binary-i386/Packages' as repository 'http://apt.llvm.org/noble llvm-toolchain-noble-17 InRelease' doesn't support architecture 'i386'

scripts/setup-ubuntu.sh

@@ -323,7 +323,7 @@ $SUDO dpkg --add-architecture i386
 $SUDO cp $(dirname "$(realpath "$0")")/llvm-snapshot.gpg.key /etc/apt/trusted.gpg.d/apt.llvm.org.asc
 $SUDO chmod a+r /etc/apt/trusted.gpg.d/apt.llvm.org.asc
 {
-	echo "deb http://apt.llvm.org/noble/ llvm-toolchain-noble-17 main"
+	echo "deb [arch=amd64] http://apt.llvm.org/noble/ llvm-toolchain-noble-17 main"
 } | $SUDO tee /etc/apt/sources.list.d/apt-llvm-org.list > /dev/null
 
 $SUDO apt-get -yq update