cgen: fix initialize error object in or_block (fix #24529)

[gchumillas]

Fixes #24529

There's no guarantee that memcpy will work correctly, since err_obj and cvar_name can be of different types. Instead of using memcpy, we declare a fresh variable and initialize its values.

All tests passed on a MacBook Pro M1:

v self
v test-self

[huly-for-github]

Connected to Huly®: V_0.6-22941

[spytheman]

Excellent. Thanks for the fix.

Please also add the failing test from the issue #24529 in vlib/v/tests/, to prevent regressions for similar cases in the future.

[gchumillas]

@spytheman the failing test described in the bug was already included here:
https://github.com/vlang/v/blob/master/vlib/v/tests/builtin_arrays/array_map_or_test.v#L115

It is exactly the same test :)

[spytheman]

i.e. the difference between you, where the test failed before, and the CI, is only in the version of the OS/compiler?

[gchumillas]

Yes, that's right. The tests failed on a MacBook Pro.