translate-c and pointer alignment

[daurnimator]

I ran zig translate-c -isystem /usr/include on lpeg's lptree.c and it successfully generated a zig file.

However, trying to build it as a library zig build-lib translated.zig results in:

/home/daurnimator/src/zig-peg/translated.zig:868:12: error: cast increases pointer alignment
    return @ptrCast([*c]Pattern, luaL_checkudata(L, idx, c"lpeg-pattern"));
           ^
/home/daurnimator/src/zig-peg/translated.zig:868:49: note: '?*c_void' has alignment 1
    return @ptrCast([*c]Pattern, luaL_checkudata(L, idx, c"lpeg-pattern"));
                                                ^
/home/daurnimator/src/zig-peg/translated.zig:868:21: note: '[*c]struct_Pattern' has alignment 8
    return @ptrCast([*c]Pattern, luaL_checkudata(L, idx, c"lpeg-pattern"));
                    ^

I assume zig translate-c needs to gain support for emitting alignment casts?

Note, this error is also reported as part of #2257 (comment)