Replace `build_all` job from `ci.yml` with `ci_linux_x64_clang.yml`. (#18107)

Cleanup relating to https://github.com/iree-org/iree/issues/16203 and
https://github.com/iree-org/iree/issues/17957.

After https://github.com/iree-org/iree/pull/18070, no jobs in `ci.yml`
are depending on the output of the `build_all` job. All jobs using the
compiler now live in `pkgci.yml` and use packages instead of the
"install dir".

* The reusable
[`build_all.yml`](https://github.com/iree-org/iree/blob/main/.github/workflows/build_all.yml)
workflow is still in use from benchmarking workflows, but those are
unmaintained and may be deleted soon.
* After this is merged I'll set the `linux_x64_clang` check to
"required", so PRs will need it to be passing before they can be merged.
* Now that `ci.yml` is pruned to just a few remaining jobs
(`build_test_all_bazel`, `build_test_runtime`, `small_runtime`,
`tracing`), we can also limit when the workflow runs at all. I've added
some `paths` patterns so this won't run on push events if only files
under `docs/` are changed, for example.
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d0a74bf..7d22051 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -27,11 +27,43 @@
 # https://docs.github.com/en/actions/hosting-your-own-runners/using-self-hosted-runners-in-a-workflow
 
 on:
-  workflow_dispatch:
-  pull_request:
   push:
     branches:
       - main
+    paths:
+      - ".github/workflows/ci.yml"
+      - ".github/workflows/setup.yml"
+      - ".bazelrc"
+      - ".bazelversion"
+      - "WORKSPACE"
+      - "CMakeLists.txt"
+      - "build_tools/**"
+      - "compiler/**"
+      - "llvm-external-projects/**"
+      - "runtime/**"
+      - "samples/**"
+      - "tests/**"
+      - "third_party/**"
+      - "tools/**"
+  pull_request:
+    branches:
+      - main
+    paths:
+      - ".github/workflows/ci.yml"
+      - ".github/workflows/setup.yml"
+      - ".bazelrc"
+      - ".bazelversion"
+      - "WORKSPACE"
+      - "CMakeLists.txt"
+      - "build_tools/**"
+      - "compiler/**"
+      - "llvm-external-projects/**"
+      - "runtime/**"
+      - "samples/**"
+      - "tests/**"
+      - "third_party/**"
+      - "tools/**"
+  workflow_dispatch:
 
 concurrency:
   # A PR number if a pull request and otherwise the commit hash. This cancels
@@ -55,16 +87,6 @@
   ################################### Basic ####################################
   # Jobs that build all of IREE "normally"
   ##############################################################################
-  # TODO(scotttodd): drop this job in favor of ci_linux_x64_clang.yml once no jobs depend on it
-  build_all:
-    needs: setup
-    if: contains(fromJson(needs.setup.outputs.enabled-jobs), 'build_all')
-    uses: ./.github/workflows/build_all.yml
-    with:
-      runner-group: ${{ needs.setup.outputs.runner-group }}
-      runner-env: ${{ needs.setup.outputs.runner-env }}
-      write-caches: ${{ needs.setup.outputs.write-caches }}
-      run-tests: true
 
   build_test_all_bazel:
     needs: setup
@@ -370,7 +392,6 @@
       - setup
 
       # Basic
-      - build_all
       - build_test_all_bazel
 
       # Accelerators
diff --git a/.github/workflows/ci_linux_x64_clang.yml b/.github/workflows/ci_linux_x64_clang.yml
index 049c268..380ce0a 100644
--- a/.github/workflows/ci_linux_x64_clang.yml
+++ b/.github/workflows/ci_linux_x64_clang.yml
@@ -7,14 +7,36 @@
 name: CI - Linux x64 clang
 
 on:
+  push:
+    branches:
+      - main
+    paths:
+      - ".github/workflows/ci_linux_x64_clang.yml"
+      - ".github/workflows/setup.yml"
+      - "CMakeLists.txt"
+      - "build_tools/**"
+      - "compiler/**"
+      - "llvm-external-projects/**"
+      - "runtime/**"
+      - "samples/**"
+      - "tests/**"
+      - "third_party/**"
+      - "tools/**"
   pull_request:
     branches:
       - main
     paths:
       - ".github/workflows/ci_linux_x64_clang.yml"
-  schedule:
-    # Weekday mornings at 09:15 UTC = 01:15 PST (UTC - 8).
-    - cron: "15 9 * * 1-5"
+      - ".github/workflows/setup.yml"
+      - "CMakeLists.txt"
+      - "build_tools/**"
+      - "compiler/**"
+      - "llvm-external-projects/**"
+      - "runtime/**"
+      - "samples/**"
+      - "tests/**"
+      - "third_party/**"
+      - "tools/**"
   workflow_dispatch:
 
 concurrency:
@@ -31,6 +53,7 @@
 
   linux_x64_clang:
     needs: setup
+    if: contains(fromJson(needs.setup.outputs.enabled-jobs), 'linux_x64_clang')
     runs-on:
       - self-hosted # must come first
       - runner-group=${{ needs.setup.outputs.runner-group }}
diff --git a/.github/workflows/ci_linux_x64_clang_asan.yml b/.github/workflows/ci_linux_x64_clang_asan.yml
index e291c5c..e634bde 100644
--- a/.github/workflows/ci_linux_x64_clang_asan.yml
+++ b/.github/workflows/ci_linux_x64_clang_asan.yml
@@ -12,6 +12,7 @@
       - main
     paths:
       - ".github/workflows/ci_linux_x64_clang_asan.yml"
+      - ".github/workflows/setup.yml"
       - "CMakeLists.txt"
       - "build_tools/**"
       - "compiler/**"
@@ -26,6 +27,7 @@
       - main
     paths:
       - ".github/workflows/ci_linux_x64_clang_asan.yml"
+      - ".github/workflows/setup.yml"
       - "CMakeLists.txt"
       - "build_tools/**"
       - "compiler/**"
diff --git a/README.md b/README.md
index 690690a..a89e14e 100644
--- a/README.md
+++ b/README.md
@@ -39,7 +39,7 @@
 
 | Host platform | Build status |
 | -- | --: |
-Linux | [![CI - Linux x64 clang](https://github.com/iree-org/iree/actions/workflows/ci_linux_x64_clang.yml/badge.svg?query=branch%3Amain+event%3Aschedule)](https://github.com/iree-org/iree/actions/workflows/ci_linux_x64_clang.yml?query=branch%3Amain+event%3Apush)<br>[![CI - Linux arm64 clang](https://github.com/iree-org/iree/actions/workflows/ci_linux_arm64_clang.yml/badge.svg?query=branch%3Amain+event%3Aschedule)](https://github.com/iree-org/iree/actions/workflows/ci_linux_arm64_clang.yml?query=branch%3Amain+event%3Aschedule)
+Linux | [![CI - Linux x64 clang](https://github.com/iree-org/iree/actions/workflows/ci_linux_x64_clang.yml/badge.svg?query=branch%3Amain+event%3Apush)](https://github.com/iree-org/iree/actions/workflows/ci_linux_x64_clang.yml?query=branch%3Amain+event%3Apush)<br>[![CI - Linux arm64 clang](https://github.com/iree-org/iree/actions/workflows/ci_linux_arm64_clang.yml/badge.svg?query=branch%3Amain+event%3Aschedule)](https://github.com/iree-org/iree/actions/workflows/ci_linux_arm64_clang.yml?query=branch%3Amain+event%3Aschedule)
 macOS | [![CI - macOS x64 clang](https://github.com/iree-org/iree/actions/workflows/ci_macos_x64_clang.yml/badge.svg?query=branch%3Amain+event%3Aschedule)](https://github.com/iree-org/iree/actions/workflows/ci_macos_x64_clang.yml?query=branch%3Amain+event%3Aschedule)
 Windows | [![CI - Windows x64 MSVC](https://github.com/iree-org/iree/actions/workflows/ci_windows_x64_msvc.yml/badge.svg?query=branch%3Amain+event%3Aschedule)](https://github.com/iree-org/iree/actions/workflows/ci_windows_x64_msvc.yml?query=branch%3Amain+event%3Aschedule)