bazel: move -std=c++14 to .bazelrc

Bazel defaults to -std=c++11 on macOS which gtest doesn't support.

.github/workflows/gtest-ci.yml

@@ -4,9 +4,6 @@ on:
   push:
   pull_request:
 
-env:
-  BAZEL_CXXOPTS: -std=c++14
-
 jobs:
   Linux:
     runs-on: ubuntu-latest
@@ -17,7 +14,7 @@ jobs:
         fetch-depth: 0
 
     - name: Tests
-      run: bazel test --cxxopt=-std=c++14 --features=external_include_paths --test_output=errors ...
+      run: bazel test --features=external_include_paths --test_output=errors ...
 
   MacOs:
     runs-on: macos-latest
@@ -28,7 +25,7 @@ jobs:
         fetch-depth: 0
 
     - name: Tests
-      run:  bazel test --cxxopt=-std=c++14 --features=external_include_paths --test_output=errors ...
+      run:  bazel test --features=external_include_paths --test_output=errors ...
 
 
   Windows:
@@ -40,4 +37,4 @@ jobs:
         fetch-depth: 0
 
     - name: Tests
-      run: bazel test --cxxopt=-std=c++14 --features=external_include_paths --test_output=errors ...
+      run: bazel test --features=external_include_paths --test_output=errors ...