Speed up net.sh builds (#16360)

* Speed up net.sh builds

* feedback

* Update net/net.sh

Co-authored-by: Tyera Eulberg <teulberg@gmail.com>

* feedback

* fix

Co-authored-by: Trent Nelson <trent.a.b.nelson@gmail.com>
Co-authored-by: Tyera Eulberg <teulberg@gmail.com>

cargo

@@ -3,25 +3,22 @@
 # shellcheck source=ci/rust-version.sh
 here=$(dirname "$0")
 
-source "${here}"/ci/rust-version.sh all
-
 toolchain=
 case "$1" in
   stable)
+    source "${here}"/ci/rust-version.sh stable
     # shellcheck disable=SC2054 # rust_stable is sourced from rust-version.sh
     toolchain="$rust_stable"
     shift
     ;;
   nightly)
+    source "${here}"/ci/rust-version.sh nightly
     # shellcheck disable=SC2054 # rust_nightly is sourced from rust-version.sh
     toolchain="$rust_nightly"
     shift
     ;;
-  +*)
-    toolchain="${1#+}"
-    shift
-    ;;
   *)
+    source "${here}"/ci/rust-version.sh stable
     # shellcheck disable=SC2054 # rust_stable is sourced from rust-version.sh
     toolchain="$rust_stable"
     ;;