ci: post: Trigger correct job, do not wait

The next job in the pipeline is _rust-cross/main_, not
_cross-rust/main_.

Also, we don't need to wait for follow-up jobs.  Otherwise, we end up
with the whole pipeline blocking the _base_ job, etc.

ci/Jenkinsfile

@@ -49,6 +49,13 @@ pipeline {
     }
 
     post {
+        success {
+            build([
+                job: "${BRANCH_NAME.replace('cross/', 'rust-cross%2F')}",
+                wait: false,
+            ])
+        }
+
         failure {
             sh 'unshare -Ur --map-auto chown root:root -R tmp log'
             dir('tmp/portage') {

crossdev.sh

@@ -23,35 +23,3 @@ EOF
 emerge -kvnj --rebuilt-binaries=y sys-devel/crossdev
 
 crossdev --stable -t "$1"
-
-ln -s /var/db/repos/gentoo/sys-devel/rust-std /var/db/repos/crossdev/cross-${target}/
-
-case ${target%%-*} in
-aarch64)
-    llvm_target=AArch64
-    ;;
-arm*)
-    llvm_target=ARM
-    ;;
-*)
-    printf 'Unknown LLVM target: %s' "${target%%-*}"
-    exit 1
-    ;;
-esac
-
-mkdir -p \
-    /etc/portage/env/dev-lang \
-    /etc/portage/package.accept_keywords \
-    /etc/portage/package.use \
-    && :
-printf 'cross-%s/rust-std **\n' "${target}" \
-    > /etc/portage/package.accept_keywords/rust-cross
-printf 'dev-lang/rust rust-src LLVM_TARGETS: %s\n' \
-    "${llvm_target}" \
-    > /etc/portage/package.use/rust-src
-printf 'RUST_CROSS_TARGETS=( %s:%s:%s )\n' \
-    "${llvm_target}" \
-    "${target}" \
-    "${target}" \
-    >> /etc/portage/env/dev-lang/rust
-emerge -vbknj cross-${target}/rust-std