Split Bazel and CMake builds into separate actions (#230)

These are pretty independent and it's useful to have different statuses for them. Additionally, this would allow running the cmake build on presubmit, since it's sufficiently fast.

The README status badge is going to need to be updated, but because of weirdnesses in our sync to upstream, that will have to be a separate PR.
diff --git a/.github/workflows/ci.yml b/.github/workflows/bazel_build.yml
similarity index 78%
rename from .github/workflows/ci.yml
rename to .github/workflows/bazel_build.yml
index c9a87c6..2ef0417 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/bazel_build.yml
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-name: Continuous Integration
+name: Bazel Build
 
 on:
   push:
@@ -21,7 +21,7 @@
       - ci-test # A branch specifically for testing CI
 
 jobs:
-  bazel:
+  linux:
     runs-on: ubuntu-18.04
     env:
       CXX: clang++
@@ -66,27 +66,3 @@
           # excluded with "notap".
           # TODO(gcmn) Enable all tests except notap once we can run them on the CI
           bazel query '//... except attr("tags", "notap", //...) except //integrations/tensorflow/e2e:vulkan_conv_test except //iree/hal/vulkan:dynamic_symbols_test except //iree/samples/rt:bytecode_module_api_test except //iree/samples/simple_embedding:simple_embedding_test' | xargs bazel test --test_env=IREE_VULKAN_DISABLE=1 --define=iree_tensorflow=true --test_output=errors
-
-  cmake:
-    runs-on: ubuntu-18.04
-    env:
-      CXX: clang++
-      CC: clang
-      PYTHON_BIN: /usr/bin/python3
-    steps:
-      - name: Installing dependencies
-        run: |
-          sudo apt-get update
-          sudo apt-get install clang libsdl2-dev python3 python3-pip
-          sudo pip install numpy
-      - name: Checking out latest version and all submodules
-        run: |
-          git config --global remote.origin.fetch '+refs/pull/*:refs/remotes/origin/pull/*'
-          git clone https://github.com/${GITHUB_REPOSITORY?} ${GITHUB_WORKSPACE?} --no-checkout --no-tags
-          git checkout ${GITHUB_SHA?}
-          git submodule update --init --depth 1000 --jobs 8
-      - name: Building with cmake
-        run: |
-          mkdir build && cd build
-          cmake -DIREE_BUILD_COMPILER=OFF -DIREE_BUILD_TESTS=ON -DIREE_BUILD_SAMPLES=OFF -DIREE_BUILD_DEBUGGER=OFF ..
-          cmake --build .
diff --git a/.github/workflows/cmake_build.yml b/.github/workflows/cmake_build.yml
new file mode 100644
index 0000000..da409ff
--- /dev/null
+++ b/.github/workflows/cmake_build.yml
@@ -0,0 +1,46 @@
+# Copyright 2019 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: CMake Build
+
+on:
+  push:
+    branches:
+      - master
+      - ci-test # A branch specifically for testing CI
+
+jobs:
+  linux:
+    runs-on: ubuntu-18.04
+    env:
+      CXX: clang++
+      CC: clang
+      PYTHON_BIN: /usr/bin/python3
+    steps:
+      - name: Installing dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install clang libsdl2-dev python3 python3-pip
+          sudo pip install numpy
+      - name: Checking out latest version and all submodules
+        run: |
+          git config --global remote.origin.fetch '+refs/pull/*:refs/remotes/origin/pull/*'
+          git clone https://github.com/${GITHUB_REPOSITORY?} ${GITHUB_WORKSPACE?} --no-checkout --no-tags
+          git checkout ${GITHUB_SHA?}
+          git submodule update --init --depth 1000 --jobs 8
+      - name: Building with cmake
+        run: |
+          mkdir build && cd build
+          cmake -DIREE_BUILD_COMPILER=OFF -DIREE_BUILD_TESTS=ON -DIREE_BUILD_SAMPLES=OFF -DIREE_BUILD_DEBUGGER=OFF ..
+          cmake --build .