Conditionalize Bionic workarounds on __ANDROID_API__

Signed-off-by: Matt Whitlock <busybox@mattwhitlock.name>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/platform.h b/include/platform.h
index 8896a6b..1706b18 100644
--- a/include/platform.h
+++ b/include/platform.h
@@ -480,10 +480,16 @@
 #endif
 
 #if defined(ANDROID) || defined(__ANDROID__)
-# undef HAVE_DPRINTF
-# undef HAVE_TTYNAME_R
-# undef HAVE_GETLINE
-# undef HAVE_STPCPY
+# if __ANDROID_API__ < 8
+#  undef HAVE_DPRINTF
+# else
+#  define dprintf fdprintf
+# endif
+# if __ANDROID_API__ < 21
+#  undef HAVE_TTYNAME_R
+#  undef HAVE_GETLINE
+#  undef HAVE_STPCPY
+# endif
 # undef HAVE_MEMPCPY
 # undef HAVE_STRCHRNUL
 # undef HAVE_STRVERSCMP