Colorize GTest Output in GitHub Actions (#1218)

Summary:
GitHub actions supports terminal colors, but most programs won't output color to a non-interactive terminal. We can control this via env variable, so that GTest output in GitHub actions is colorized.

Before:
{F847577544}

After:
{F847577610}

Pull Request resolved: https://github.com/facebook/yoga/pull/1218

Reviewed By: christophpurrer

Differential Revision: D42537630

Pulled By: NickGerleman

fbshipit-source-id: 28b22c061200026bf167c1a31d6a58445ba70214

.github/workflows/validate-cpp.yml

@@ -7,6 +7,9 @@ on:
       - main
   workflow_dispatch:
 
+env:
+  GTEST_COLOR: 1
+
 jobs:
   test:
     name: Build and Test [${{ matrix.os }}][${{ matrix.mode }}]