Convert experimental flags to incompatible

This cl converts their experimental siblings into:

`--incompatible_dont_emit_static_libgcc`
(#6825)

`--incompatible_linkopts_in_user_link_flags`
(#6826)

RELNOTES:
Added `--incompatible_dont_emit_static_libgcc` (#6825)
Added `--incompatible_linkopts_in_user_link_flags` (#6826)
PiperOrigin-RevId: 223938818

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

@@ -723,22 +723,30 @@ public Label getFdoPrefetchHintsLabel() {
   public boolean disableLegacyCrosstoolFields;
 
   @Option(
-      name = "experimental_linkopts_in_user_link_flags",
+      name = "incompatible_linkopts_in_user_link_flags",
+      oldName = "experimental_linkopts_in_user_link_flags",
       defaultValue = "false",
-      documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
+      documentationCategory = OptionDocumentationCategory.TOOLCHAIN,
       effectTags = {OptionEffectTag.ACTION_COMMAND_LINES, OptionEffectTag.LOADING_AND_ANALYSIS},
-      metadataTags = {OptionMetadataTag.EXPERIMENTAL},
+      metadataTags = {
+        OptionMetadataTag.INCOMPATIBLE_CHANGE,
+        OptionMetadataTag.TRIGGERED_BY_ALL_INCOMPATIBLE_CHANGES
+      },
       help =
           "If true, flags coming from --linkopt Bazel option will appear in user_link_flags "
-              + "crosstool variable.")
+              + "crosstool variable, not in legacy_link_flags.")
   public boolean enableLinkoptsInUserLinkFlags;
 
   @Option(
-      name = "experimental_dont_emit_static_libgcc",
+      name = "incompatible_dont_emit_static_libgcc",
+      oldName = "experimental_dont_emit_static_libgcc",
       defaultValue = "false",
-      documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
+      documentationCategory = OptionDocumentationCategory.TOOLCHAIN,
       effectTags = {OptionEffectTag.ACTION_COMMAND_LINES, OptionEffectTag.LOADING_AND_ANALYSIS},
-      metadataTags = {OptionMetadataTag.EXPERIMENTAL},
+      metadataTags = {
+        OptionMetadataTag.INCOMPATIBLE_CHANGE,
+        OptionMetadataTag.TRIGGERED_BY_ALL_INCOMPATIBLE_CHANGES
+      },
       help =
           "If true, bazel will not add --static-libgcc to the linking command line, it will be "
               + "the responsibility of the C++ toolchain to append this flag.")