vlc_fixups: don't declare swab() on Android NDK25

Fix build on Android NDK25, where swab() is a static inline function
defined in <unistd.h>.

include/vlc_fixups.h

@@ -375,8 +375,11 @@ extern "C" {
 #endif
 
 #ifndef HAVE_SWAB
+/* Android NDK25 have swab but configure fails to detect it */
+#ifndef __ANDROID__
 void swab (const void *, void *, ssize_t);
 #endif
+#endif
 
 /* Socket stuff */
 #ifndef HAVE_INET_PTON