Re-hide some error.h stuff.

Bug: https://github.com/android/ndk/issues/2081
Test: vcpkg install --triple=arm64-android gsasl
Change-Id: If47f2676c312cd5e6a699b2fa0a2ce86a6f8724b
diff --git a/libc/include/error.h b/libc/include/error.h
index cb867cd..4d6a965 100644
--- a/libc/include/error.h
+++ b/libc/include/error.h
@@ -37,6 +37,9 @@
 
 __BEGIN_DECLS
 
+// These cause issues with gnulib's polyfill
+// https://github.com/android/ndk/issues/2081
+#if __ANDROID_API__ >= 23
 /**
  * [error_print_progname(3)](https://man7.org/linux/man-pages/man3/error_print_progname.3.html) is
  * a function pointer that, if non-null, is called by error() instead of prefixing errors with the
@@ -45,7 +48,9 @@
  * Available since API level 23.
  */
 extern void (* _Nullable error_print_progname)(void) __INTRODUCED_IN(23);
+#endif
 
+#if __ANDROID_API__ >= 23
 /**
  * [error_message_count(3)](https://man7.org/linux/man-pages/man3/error_message_count.3.html) is
  * a global count of the number of calls to error() and error_at_line().
@@ -53,6 +58,7 @@
  * Available since API level 23.
  */
 extern unsigned int error_message_count __INTRODUCED_IN(23);
+#endif
 
 /**
  * [error_one_per_line(3)](https://man7.org/linux/man-pages/man3/error_one_per_line.3.html) is