Export libcore aconfig flags to frameworks-minus-apex bootclasspath

The DateIntervalFormatTest.testIsLibcoreVFlagEnabled() doesn't pass in AOSP today, even though `printflags` shows `core_libraries/com.android.libcore.v_apis: READ_ONLY + ENABLED (/apex/com.android.art)`. So try to submit it in internal main instead.

Bug: 349108429
Test: atest FrameworksCoreTests:android.text.format.DateIntervalFormatTest
Flag: EXEMPT Add exported flag lib
Change-Id: I6244a615ae3d1c82bcf367c6e06994741c0553bb
diff --git a/AconfigFlags.bp b/AconfigFlags.bp
index a16aa2d..da3f172 100644
--- a/AconfigFlags.bp
+++ b/AconfigFlags.bp
@@ -98,6 +98,7 @@
         "framework-jobscheduler-job.flags-aconfig-java",
         "framework_graphics_flags_java_lib",
         "hwui_flags_java_lib",
+        "libcore_exported_aconfig_flags_lib",
         "power_flags_lib",
         "sdk_sandbox_flags_lib",
         "surfaceflinger_flags_java_lib",
@@ -140,6 +141,14 @@
     defaults: ["framework-minus-apex-aconfig-java-defaults"],
 }
 
+// Core Libraries / libcore
+java_aconfig_library {
+    name: "libcore_exported_aconfig_flags_lib",
+    aconfig_declarations: "libcore-aconfig-flags",
+    mode: "exported",
+    defaults: ["framework-minus-apex-aconfig-java-defaults"],
+}
+
 // Telecom
 java_aconfig_library {
     name: "telecom_flags_core_java_lib",