Wire up _weak posix_fadvise()

The commit adding Android support included a botched
variant of posix_fadvise().

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/helpers.c b/helpers.c
index 5be45cc..1b4e1d0 100644
--- a/helpers.c
+++ b/helpers.c
@@ -50,3 +50,10 @@
 	return -1;
 }
 #endif
+
+#ifndef FIO_HAVE_FADVISE
+int _weak posix_fadvise(int fd, off_t offset, off_t len, int advice)
+{
+	return 0;
+}
+#endif
diff --git a/helpers.h b/helpers.h
index ed2086d..191096b 100644
--- a/helpers.h
+++ b/helpers.h
@@ -15,5 +15,6 @@
 extern int _weak clock_gettime(clockid_t clk_id, struct timespec *ts);
 extern int _weak sync_file_range(int fd, off64_t offset, off64_t nbytes,
 					unsigned int flags);
+extern int _weak posix_fadvise(int fd, off_t offset, off_t len, int advice);
 
 #endif /* FIO_HELPERS_H_ */
diff --git a/os/os.h b/os/os.h
index dd70464..2e4764e 100644
--- a/os/os.h
+++ b/os/os.h
@@ -68,22 +68,11 @@
 #define OS_MSG_DONTWAIT	MSG_DONTWAIT
 #endif
 
-#ifndef FIO_HAVE_FADVISE
-static inline int posix_fadvise(int fd, int off, int len, int advice)
-{
-	(void)fd;
-	(void)off;
-	(void)len;
-	(void)advice;
-	return 0;
-}
-
 #ifndef POSIX_FADV_DONTNEED
 #define POSIX_FADV_DONTNEED	(0)
 #define POSIX_FADV_SEQUENTIAL	(0)
 #define POSIX_FADV_RANDOM	(0)
 #endif
-#endif /* FIO_HAVE_FADVISE */
 
 #ifndef FIO_HAVE_CPU_AFFINITY
 #define fio_setaffinity(pid, mask)	(0)