Update env vars in bat files

build.bat

@@ -1,5 +1,5 @@
 @echo off
-rem We're not really on Azure Pipelines but this disables the Cassandra node requirement
-set TF_BUILD=True
+rem We're not really on GitHub Actions but this disables the Cassandra node requirement
+set GITHUB_ACTIONS=true
 powershell -ExecutionPolicy Bypass build\build.ps1 -Script build\build.cake -Target Build
 pause

execute-tests.bat

@@ -1,5 +1,5 @@
 @echo off
-rem We're not really on Azure Pipelines but this disables the Cassandra node requirement
-set TF_BUILD=True
+rem We're not really on GitHub Actions but this disables the Cassandra node requirement
+set GITHUB_ACTIONS=true
 powershell -ExecutionPolicy Bypass build\build.ps1 -Script build\build.cake -Target Test
 pause