fix arm64 alignment issues in signal()

Author: ryanschneider

src/cstd.zig

@@ -536,12 +536,12 @@ export fn strerror(errnum: c_int) callconv(.C) [*:0]const u8 {
 // --------------------------------------------------------------------------------
 const SignalFn = switch (builtin.zig_backend) {
     .stage1 => fn(c_int) callconv(.C) void,
-    else => *const fn(c_int) callconv(.C) void,
+    else => *align(1) const fn(c_int) callconv(.C) void,
 };
 export fn signal(sig: c_int, func: SignalFn) callconv(.C) ?SignalFn {
     if (builtin.os.tag == .linux) {
         var action = std.os.Sigaction{
-            .handler = .{ .handler = func },
+            .handler = .{ .handler = @alignCast(@alignOf(fn(c_int) callconv(.C) void), func) },
             .mask = std.os.linux.empty_sigset,
             .flags = std.os.SA.RESTART,
             .restorer = null,