Pin the compiler version used in this workspace and for CI workflows. (#114)

diff --git a/.bazelrc b/.bazelrc
index f9ed7d2..80fb404 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -13,8 +13,8 @@
 # limitations under the License.
 
 # Force the use of Clang for all builds.
-build --action_env=CC=clang
-build --action_env=CXX=clang++
+build --action_env=CC=clang-10
+build --action_env=CXX=clang++-10
 
 # The ASAN configuration suitable for C++ unit tests.
 build:asan --copt=-fsanitize=address
diff --git a/.github/workflows/bazel_test.yml b/.github/workflows/bazel_test.yml
index ba991b1..286f408 100644
--- a/.github/workflows/bazel_test.yml
+++ b/.github/workflows/bazel_test.yml
@@ -24,6 +24,12 @@
     steps:
       - name: Checkout repository
         uses: actions/checkout@v2
+      - name: Install dependencies
+        run: |
+          sudo apt-get update && sudo apt-get install -yq \
+            clang-10 \
+            libunwind-dev \
+            libblocksruntime-dev
       - name: Run unit tests
         run: |
           bazel test --test_tag_filters=-fuzz-test --build_tests_only //...
@@ -46,7 +52,11 @@
       - name: Checkout repository
         uses: actions/checkout@v2
       - name: Install dependencies
-        run: sudo apt-get update && sudo apt-get install -yq libunwind-dev libblocksruntime-dev
+        run: |
+          sudo apt-get update && sudo apt-get install -yq \
+            clang-10 \
+            libunwind-dev \
+            libblocksruntime-dev
       - name: Run smoke test
         run: |
           bazel run ${{ matrix.target }} --config=${{ matrix.config }} -- --clean --timeout_secs=5
@@ -61,7 +71,11 @@
       - name: Checkout repository
         uses: actions/checkout@v2
       - name: Install dependencies
-        run: sudo apt-get update && sudo apt-get install -yq libunwind-dev libblocksruntime-dev
+        run: |
+          sudo apt-get update && sudo apt-get install -yq \
+            clang-10 \
+            libunwind-dev \
+            libblocksruntime-dev
       - name: Run regression tests
         run: |
           bazel test --verbose_failures --test_output=all \