Don't let the test exec group inherit from the default exec group

Part of #24964.

RELNOTES[INC]: Constraints and toolchain requirements added to the default exec group, for example via the toolchains parameter of the rule function or the exec_compatible_with attribute on all rules, no longer apply to the test exec group, which contains the test action on test rules. Instead, use exec_group_compatible_with to apply constraints and/or define an explicit test exec group with toolchain requirements on test rules that require it.

PiperOrigin-RevId: 721834175
Change-Id: I8504ff1a08a643ed35a7282f09f6d6faf75d574c

src/main/java/com/google/devtools/build/lib/packages/RuleClass.java

@@ -162,7 +162,10 @@ public class RuleClass implements RuleClassData {
   public static final String APPLICABLE_METADATA_ATTR_ALT = "applicable_licenses";
 
   public static final String DEFAULT_TEST_RUNNER_EXEC_GROUP_NAME = "test";
-  public static final ExecGroup DEFAULT_TEST_RUNNER_EXEC_GROUP = ExecGroup.COPY_FROM_DEFAULT;
+  // The test exec group should not inherit any exec constraints or toolchains from the default exec
+  // group since the execution platform for a test is generally independent (and often different)
+  // from the execution platform of the actions that produce the test executable.
+  public static final ExecGroup DEFAULT_TEST_RUNNER_EXEC_GROUP = ExecGroup.builder().build();
 
   /** Interface for determining whether a rule needs toolchain resolution or not. */
   @FunctionalInterface

src/test/java/com/google/devtools/build/lib/analysis/StarlarkExecGroupTest.java

@@ -813,10 +813,6 @@ def _impl(ctx):
             name = "gpu_platform",
             constraint_values = [
                 "CONSTRAINTS_PACKAGE_ROOTos:linux",
-                # TODO: This constraint should not be needed, it's only required
-                # because default exec constraints implicitly leak into the
-                # 'test' exec group.
-                ":has_fast_cpu",
                 ":has_gpu",
             ],
             exec_properties = {