v1.18: ci: don't self-update rustup when using the rust-version scrip…

…t (backport of anza-xyz#1209) (anza-xyz#1215)

ci: don't self-update rustup when using the rust-version script (anza-xyz#1209)

* ci: don't update rustup when using the rust-version script

* XXX: fake updates for triggering all

* Revert "XXX: fake updates for triggering all"

This reverts commit b343e61.

(cherry picked from commit 206a87a)

Co-authored-by: Yihau Chen <yihau.chen@icloud.com>

ci/rust-version.sh

@@ -45,7 +45,7 @@ export rust_nightly_docker_image=solanalabs/rust-nightly:"$nightly_version"
     declare toolchain=$1
     if ! cargo +"$toolchain" -V > /dev/null; then
       echo "$0: Missing toolchain? Installing...: $toolchain" >&2
-      rustup install "$toolchain"
+      rustup install "$toolchain" --no-self-update
       cargo +"$toolchain" -V
     fi
   }