Fix alignment error in Interface.downcast when compiling for 32-bit

[spookee0]

Got this error when my struct became 8-aligned:

❯ zig build
install
└─ compile exe fw.elf Debug thumb-freestanding-eabihf 1 errors
<cache>/zigfsm-0.2.0-9VW4ufo6AQDk-HL7-JMc-XNgKRXzkeoNdDzrMtg8eF45/src/main.zig:647:16: error: @fieldParentPtr increases pointer alignment
        return @fieldParentPtr(field_name, interface_ref);
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<cache>/zigfsm-0.2.0-9VW4ufo6AQDk-HL7-JMc-XNgKRXzkeoNdDzrMtg8eF45/src/main.zig:647:16: note: '*align(4) Bldc' has alignment '4'
<cache>/zigfsm-0.2.0-9VW4ufo6AQDk-HL7-JMc-XNgKRXzkeoNdDzrMtg8eF45/src/main.zig:647:16: note: '*Bldc' has alignment '8'
<cache>/zigfsm-0.2.0-9VW4ufo6AQDk-HL7-JMc-XNgKRXzkeoNdDzrMtg8eF45/src/main.zig:647:16: note: use @alignCast to assert pointer alignment
referenced by:
    onTransition: src/Bldc.zig:97:50
    make [inlined]: <cache>/zigfsm-0.2.0-9VW4ufo6AQDk-HL7-JMc-XNgKRXzkeoNdDzrMtg8eF45/src/main.zig:656:44
    init [inlined]: src/Bldc.zig:37:46
    bldc: src/Starter.zig:3:34
    8 reference(s) hidden; use '-freference-trace=12' to see all references
error: the following command failed with 1 compilation errors:
<toolchain>/zig build-exe ...

Found this: https://ziggit.dev/t/is-aligncast-necessary-with-fieldparentptr/11902/2
and this is my case (32-bit cortex-m4)

With @alignCast my code compiles and works as before

[cryptocode]

Good catch, thanks!