Fix runtime interface tests on Windows

[bkchr]

Fixes: #4800

[Swader]

Different error, previous location seems to pass now.

    Checking parity-util-mem v0.3.0
error[E0308]: mismatched types
  --> C:\Users\Bruno\.cargo\registry\src\github.aaakk.us.kg-1ecc6299db9ec823\parity-util-mem-0.3.0\src\allocators.rs:84:30
   |
84 |                 if HeapValidate(heap, 0, ptr) == 0 {
   |                                          ^^^ expected enum `winapi::ctypes::c_void`, found enum `std::ffi::c_void`
   |
   = note: expected raw pointer `*const winapi::ctypes::c_void`
              found raw pointer `*const std::ffi::c_void`

error[E0308]: mismatched types
  --> C:\Users\Bruno\.cargo\registry\src\github.aaakk.us.kg-1ecc6299db9ec823\parity-util-mem-0.3.0\src\allocators.rs:88:23
   |
88 |                 HeapSize(heap, 0, ptr) as usize
   |                                   ^^^ expected enum `winapi::ctypes::c_void`, found enum `std::ffi::c_void`
   |
   = note: expected raw pointer `*const winapi::ctypes::c_void`
              found raw pointer `*const std::ffi::c_void`

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0308`.
error: could not compile `parity-util-mem`.
warning: build failed, waiting for other jobs to finish...
error: build failed
test ui ... FAILED

failures:

---- ui stdout ----
thread 'ui' panicked at 'tests failed', C:\Users\Bruno\.cargo\registry\src\github.aaakk.us.kg-1ecc6299db9ec823\trybuild-1.0.21\src\run.rs:38:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.


failures:
    ui

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out

error: test failed, to rerun pass '-p sp-runtime-interface --test ui'

[kianenigma]

if the error is coming from \parity-util-mem, we are using it in substrate as well (not just soon) as of #4822.

[bkchr]

Yeah, it seems that there are more problems that needs further fixing. However this small one makes it compile at least.