Update SkyframeTests to not rely on filegroup not using toolchain

resolution.

Part of work on bazelbuild#12899.

Closes bazelbuild#12907.

PiperOrigin-RevId: 353937486

src/test/java/com/google/devtools/build/lib/skyframe/RegisteredExecutionPlatformsFunctionTest.java

@@ -221,7 +221,8 @@ public void testRegisteredExecutionPlatforms_targetPattern_flagOverride() throws
   @Test
   public void testRegisteredExecutionPlatforms_notExecutionPlatform() throws Exception {
     rewriteWorkspace("register_execution_platforms(", "    '//error:not_an_execution_platform')");
-    scratch.file("error/BUILD", "filegroup(name = 'not_an_execution_platform')");
+    // Have to use a rule that doesn't require a target platform, or else there will be a cycle.
+    scratch.file("error/BUILD", "toolchain_type(name = 'not_an_execution_platform')");
 
     // Request the executionPlatforms.
     SkyKey executionPlatformsKey = RegisteredExecutionPlatformsValue.key(targetConfigKey);

src/test/java/com/google/devtools/build/lib/skyframe/ToolchainResolutionFunctionTest.java

@@ -299,7 +299,8 @@ public void resolve_invalidHostPlatform() throws Exception {
 
   @Test
   public void resolve_invalidExecutionPlatform() throws Exception {
-    scratch.file("invalid/BUILD", "filegroup(name = 'not_a_platform')");
+    // Have to use a rule that doesn't require a target platform, or else there will be a cycle.
+    scratch.file("invalid/BUILD", "toolchain_type(name = 'not_a_platform')");
     useConfiguration("--extra_execution_platforms=//invalid:not_a_platform");
     ToolchainContextKey key =
         ToolchainContextKey.key()