Merge pull request #61 from akiss77/fix-aarch64-syscall

Fix getrandom syscall number for aarch64-unknown-linux-gnu
diff --git a/src/os.rs b/src/os.rs
index c0f875c..2be1687 100644
--- a/src/os.rs
+++ b/src/os.rs
@@ -40,8 +40,10 @@
         const NR_GETRANDOM: libc::c_long = 318;
         #[cfg(target_arch = "x86")]
         const NR_GETRANDOM: libc::c_long = 355;
-        #[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
+        #[cfg(target_arch = "arm")]
         const NR_GETRANDOM: libc::c_long = 384;
+        #[cfg(target_arch = "aarch64")]
+        const NR_GETRANDOM: libc::c_long = 278;
         #[cfg(target_arch = "powerpc")]
         const NR_GETRANDOM: libc::c_long = 384;