llvmPackages: 16.0.6 -> 17.0.6 on Linux

rustc is already using LLVM 17, so as long as we don't find that
anything widely used part of a NixOS system has a hard requirement of
LLVM 16 over LLVM 17, it makes sense to upgrade the default to
minimise the number of LLVMs in closures.

All my systems build fine with LLVM 17 as the default.

pkgs/top-level/all-packages.nix

@@ -16542,7 +16542,7 @@ with pkgs;
       /**/ if platform.isDarwin then 16
       else if platform.isFreeBSD then 12
       else if platform.isAndroid then 12
-      else if platform.isLinux then 16
+      else if platform.isLinux then 17
       else if platform.isWasm then 16
       # For unknown systems, assume the latest version is required.
       else 17;