Auto merge of #1435 - dianpopa:master, r=gnzlbg

Add missing syscalls for aarch64-unknown-linux-musl

The list of syscalls from [rust-lang-aarch64-musl-syscalls](../blob/master/src/unix/notbsd/linux/musl/b64/aarch64.rs) misses some of the syscalls that are defined in [musl-libc-aarch64-syscalls](https://git.musl-libc.org/cgit/musl/tree/arch/aarch64/bits/syscall.h.in).
We need this so that we get rid of hardcoding them inside [our project](https://github.com/firecracker-microvm/firecracker/blob/master/vmm/src/default_syscalls/filters.rs#L16).

Signed-off-by: Diana Popa <dpopa@amazon.com>

Author: bors

src/unix/linux_like/linux/musl/b64/aarch64.rs

@@ -96,6 +96,7 @@ pub const SYS_epoll_ctl: ::c_long = 21;
 pub const SYS_epoll_pwait: ::c_long = 22;
 pub const SYS_dup: ::c_long = 23;
 pub const SYS_dup3: ::c_long = 24;
+pub const SYS_fcntl: ::c_long = 25;
 pub const SYS_inotify_init1: ::c_long = 26;
 pub const SYS_inotify_add_watch: ::c_long = 27;
 pub const SYS_inotify_rm_watch: ::c_long = 28;
@@ -128,6 +129,7 @@ pub const SYS_vhangup: ::c_long = 58;
 pub const SYS_pipe2: ::c_long = 59;
 pub const SYS_quotactl: ::c_long = 60;
 pub const SYS_getdents64: ::c_long = 61;
+pub const SYS_lseek: ::c_long = 62;
 pub const SYS_read: ::c_long = 63;
 pub const SYS_write: ::c_long = 64;
 pub const SYS_readv: ::c_long = 65;
@@ -143,6 +145,8 @@ pub const SYS_vmsplice: ::c_long = 75;
 pub const SYS_splice: ::c_long = 76;
 pub const SYS_tee: ::c_long = 77;
 pub const SYS_readlinkat: ::c_long = 78;
+pub const SYS_newfstatat: ::c_long = 79;
+pub const SYS_fstat: ::c_long = 80;
 pub const SYS_sync: ::c_long = 81;
 pub const SYS_fsync: ::c_long = 82;
 pub const SYS_fdatasync: ::c_long = 83;
@@ -284,6 +288,7 @@ pub const SYS_request_key: ::c_long = 218;
 pub const SYS_keyctl: ::c_long = 219;
 pub const SYS_clone: ::c_long = 220;
 pub const SYS_execve: ::c_long = 221;
+pub const SYS_mmap: ::c_long = 222;
 pub const SYS_swapon: ::c_long = 224;
 pub const SYS_swapoff: ::c_long = 225;
 pub const SYS_mprotect: ::c_long = 226;