Install xargo using CI dictated cargo version if available (#9068)

ci/rust-version.sh

@@ -38,6 +38,7 @@ export rust_nightly_docker_image=solanalabs/rust-nightly:"$nightly_version"
     declare toolchain=$1
     if ! cargo +"$toolchain" -V; then
       rustup install "$toolchain"
+      rustup default "$toolchain"
       cargo +"$toolchain" -V
     fi
   }

sdk/bpf/scripts/install.sh

@@ -22,12 +22,10 @@ download() {
   wget "${args[@]}"
 }
 
-# Install or upgrade xargo
+# Install xargo
 (
-  cargo install cargo-update
-  cargo install-update-config --version =0.3.19 xargo
-  set -e
-  cargo install-update -i xargo
+  set -ex
+  cargo +"${rust_stable:-}" install xargo
   xargo --version > xargo.md 2>&1
 )
 # shellcheck disable=SC2181