[ci] Remove unused generate-buildkite-pipeline-scheduled script (#79320)

The "scheduled build" pipeline on BuildKite had been disabled for months
and doesn't exist anymore, so this script is effectively dead code. When
we set up a cron-activated build again, we should do it using Github
actions (which could trigger a BK pipeline if needed).

Keeping this script around just creates additional confusion about
what's used and what's not used for doing CI.

.ci/generate-buildkite-pipeline-scheduled

@@ -1,81 +0,0 @@
-#!/usr/bin/env bash
-#===----------------------------------------------------------------------===##
-#
-# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-# See https://llvm.org/LICENSE.txt for license information.
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-#
-#===----------------------------------------------------------------------===##
-
-#
-# This file generates a Buildkite pipeline that triggers the various CI jobs for
-# the LLVM project on scheduled builds.
-#
-# See https://buildkite.com/docs/agent/v3/cli-pipeline#pipeline-format.
-#
-
-set -eu
-set -o pipefail
-
-# Filter rules for generic windows tests
-: ${WINDOWS_AGENTS:='{"queue": "windows"}'}
-# Filter rules for generic linux tests
-: ${LINUX_AGENTS:='{"queue": "linux"}'}
-# Set by buildkite
-: ${BUILDKITE_MESSAGE:=}
-: ${BUILDKITE_COMMIT:=}
-: ${BUILDKITE_BRANCH:=}
-
-cat <<EOF
-steps:
-  - trigger: "libcxx-ci"
-    build:
-      message: "${BUILDKITE_MESSAGE}"
-      commit: "${BUILDKITE_COMMIT}"
-      branch: "${BUILDKITE_BRANCH}"
-
-  - trigger: "clang-ci"
-    build:
-      message: "${BUILDKITE_MESSAGE}"
-      commit: "${BUILDKITE_COMMIT}"
-      branch: "${BUILDKITE_BRANCH}"
-
-  - label: ':linux: Linux x64'
-    artifact_paths:
-    - 'artifacts/**/*'
-    - '*_result.json'
-    - 'build/test-results.xml'
-    agents: ${LINUX_AGENTS}
-    retry:
-      automatic:
-        - exit_status: -1  # Agent was lost
-          limit: 2
-        - exit_status: 255 # Forced agent shutdown
-          limit: 2
-    timeout_in_minutes: 120
-    env:
-      CC: 'clang'
-      CXX: 'clang++'
-    commands:
-    - ./.ci/monolithic-linux.sh "bolt;clang;clang-tools-extra;compiler-rt;flang;libc;libclc;lld;llvm;mlir;polly;pstl" "check-all"
-
-  - label: ':windows: Windows x64'
-    artifact_paths:
-    - 'artifacts/**/*'
-    - '*_result.json'
-    - 'build/test-results.xml'
-    agents: ${WINDOWS_AGENTS}
-    retry:
-      automatic:
-        - exit_status: -1  # Agent was lost
-          limit: 2
-        - exit_status: 255 # Forced agent shutdown
-          limit: 2
-    timeout_in_minutes: 150
-    env:
-      CC: 'cl'
-      CXX: 'cl'
-      LD: 'link'
-    commands:
-    - C:\\BuildTools\\Common7\\Tools\\VsDevCmd.bat -arch=amd64 -host_arch=amd64
-    - bash .ci/monolithic-windows.sh "clang;clang-tools-extra;flang;libclc;lld;llvm;mlir;polly;pstl" "check-all"