Can't make recent ppx_inline_test work on Windows

I'm trying to make `ppx_inline_test.v0.12.0` work on Windows. To enable tests it uses
```C
CAMLprim CAMLweakdef value Base_am_testing()
{
return Val_false;
}
```
that is overridden in `ppx_inline_test`. The problem is that `CAMLweakdef` is no-op under Windows and the linker always takes `base` variant (`base.cma` goes before `ppx_inline_test_lib.cma`) so tests are always disabled. Any idea how to work around this?

Start by reproducing the Windows build with ppx_inline_test.v0.12.0 and inspect how CAMLweakdef behaves when base.cma is linked before ppx_inline_test_lib.cma. Verify a workaround that enables inline tests on Windows and confirm that the resulting test setup no longer selects the base variant.

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