Adds a conditional to the github workflow file so it only runs on the main repo

.github/workflows/cmake.yml

@@ -12,6 +12,7 @@ env:
 
 jobs:
   build:
+    if: github.repository == 'TorqueGameEngines/Torque3D'
     # The CMake configure and build commands are platform agnostic and should work equally well on Windows or Mac.
     # You can convert this to a matrix build if you need cross-platform coverage.
     # See: https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/managing-complex-workflows#using-a-build-matrix