Linux: Map Alpha getx*id to their regularly named versions

These syscalls also store the value of `euid/egid/ppid` in `r20`, but
are otherwise the same.

lib/std/os/linux.zig

@@ -2266,10 +2266,7 @@ pub fn getsid(pid: pid_t) usize {
 
 pub fn getpid() pid_t {
     // Casts result to a pid_t, safety-checking >= 0, because getpid() cannot fail
-    return @intCast(@as(u32, @truncate(syscall0(comptime switch (native_arch) {
-        .alpha => .getxpid,
-        else => .getpid,
-    }))));
+    return @intCast(@as(u32, @truncate(syscall0(.getpid))));
 }
 
 pub fn getppid() pid_t {

lib/std/os/linux/syscalls.zig

@@ -5872,11 +5872,11 @@ pub const Alpha = enum(usize) {
     brk = 17,
     osf_getfsstat = 18,
     lseek = 19,
-    getxpid = 20,
+    getpid = 20,
     osf_mount = 21,
     umount2 = 22,
     setuid = 23,
-    getxuid = 24,
+    getuid = 24,
     exec_with_loader = 25,
     ptrace = 26,
     osf_nrecvmsg = 27,
@@ -5899,7 +5899,7 @@ pub const Alpha = enum(usize) {
     osf_profil = 44,
     open = 45,
     osf_old_sigaction = 46,
-    getxgid = 47,
+    getgid = 47,
     osf_sigprocmask = 48,
     osf_getlogin = 49,
     osf_setlogin = 50,

tools/generate_linux_syscalls.zig

@@ -28,6 +28,11 @@ const stdlib_renames = std.StaticStringMap([]const u8).initComptime(.{
     // ARM EABI/Thumb.
     .{ "arm_sync_file_range", "sync_file_range" },
     .{ "arm_fadvise64_64", "fadvise64_64" },
+    // Alpha
+    // See https://github.com/torvalds/linux/blob/8bf22c33e7a172fbc72464f4cc484d23a6b412ba/arch/alpha/include/uapi/asm/unistd.h#L10
+    .{ "getxpid", "getpid" },
+    .{ "getxuid", "getuid" },
+    .{ "getxgid", "getgid" },
 });
 
 /// Filter syscalls that aren't actually syscalls.