Automated rollback of commit 8d1a324.

*** Reason for rollback ***

Broke buildkite: https://buildkite.com/bazel/bazel-with-downstream-projects-bazel/builds/503

*** Original change description ***

Flip --incompatible_disable_legacy_cpp_toolchain_skylark_api incompatible flag.

#6380

RELNOTES: Incompatible flag --incompatible_disable_legacy_cpp_toolchain_skylark_api was flipped.
PiperOrigin-RevId: 217275296

src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java

@@ -738,7 +738,7 @@ public Label getFdoPrefetchHintsLabel() {
 
   @Option(
       name = "incompatible_disable_legacy_cpp_toolchain_skylark_api",
-      defaultValue = "true",
+      defaultValue = "false",
       documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
       effectTags = {OptionEffectTag.LOADING_AND_ANALYSIS},
       metadataTags = {
@@ -920,8 +920,6 @@ public FragmentOptions getHost() {
     host.fdoProfileLabel = null;
     host.inmemoryDotdFiles = inmemoryDotdFiles;
 
-    host.disableLegacyToolchainSkylarkApi = disableLegacyToolchainSkylarkApi;
-
     return host;
   }
 

src/test/java/com/google/devtools/build/lib/rules/cpp/CcToolchainProviderTest.java

@@ -122,6 +122,26 @@ public void testDisablingLinkOptions() throws Exception {
     testDisablingLinkingApiMethod("provider.link_options_do_not_use");
   }
 
+  @Test
+  public void testDisablingMostlyStaticLinkOptionsFromConfiguration() throws Exception {
+    testDisablingLinkingApiMethod("ctx.fragments.cpp.mostly_static_link_options([], False)");
+  }
+
+  @Test
+  public void testDisablingFullyStaticLinkOptionsFromConfiguration() throws Exception {
+    testDisablingLinkingApiMethod("ctx.fragments.cpp.fully_static_link_options([], True)");
+  }
+
+  @Test
+  public void testDisablingDynamicLinkOptionsFromConfiguration() throws Exception {
+    testDisablingLinkingApiMethod("ctx.fragments.cpp.dynamic_link_options([], False)");
+  }
+
+  @Test
+  public void testDisablingLinkOptionsFromConfiguration() throws Exception {
+    testDisablingLinkingApiMethod("ctx.fragments.cpp.link_options");
+  }
+
   private void testDisablingLinkingApiMethod(String method) throws Exception {
     useConfiguration("--experimental_disable_legacy_cc_linking_api");
     testDisablingLinkingApiMethodWithConfiguration(method);
@@ -173,6 +193,27 @@ public void testDisablingCOptions() throws Exception {
   public void testDisablingUnfilteredOptions() throws Exception {
     testDisablingCompilationApiMethod("provider.unfiltered_compiler_options([])");
   }
+
+  @Test
+  public void testDisablingCompilerOptionsFromConfiguration() throws Exception {
+    testDisablingCompilationApiMethod("ctx.fragments.cpp.compiler_options([])");
+  }
+
+  @Test
+  public void testDisablingCxxOptionsFromConfiguration() throws Exception {
+    testDisablingCompilationApiMethod("ctx.fragments.cpp.cxx_options([])");
+  }
+
+  @Test
+  public void testDisablingCOptionsFromConfiguration() throws Exception {
+    testDisablingCompilationApiMethod("ctx.fragments.cpp.c_options");
+  }
+
+  @Test
+  public void testDisablingUnfilteredOptionsFromConfiguration() throws Exception {
+    testDisablingCompilationApiMethod("ctx.fragments.cpp.unfiltered_compiler_options([])");
+  }
+
   private void testDisablingCompilationApiMethod(String method) throws Exception {
     useConfiguration("--experimental_disable_legacy_cc_compilation_api");
     testDisablingCompilationApiMethodWithConfiguration(method);