Fix cosmwasm-vm tests on windows

[devashishdxt]

There are 2 major changes:

• Created windows symlinks for wasm files as windows does not recognize linux symlinks.
• Windows returns different error message when file not found.

[tomtau]

ditto: CosmWasm/wasmvm#338 (comment)

[devashishdxt]

This function gets called at 3 places from wasmd:

1. During ExportGenesis: https://github.com/CosmWasm/wasmd/blob/82130463ad6d72548aabd7a2e7daf0d2a9b645dc/x/wasm/keeper/genesis.go#L91
2. During Snapshot: https://github.com/CosmWasm/wasmd/blob/82130463ad6d72548aabd7a2e7daf0d2a9b645dc/x/wasm/keeper/snapshotter.go#L68
3. During Query: https://github.com/CosmWasm/wasmd/blob/82130463ad6d72548aabd7a2e7daf0d2a9b645dc/x/wasm/keeper/querier.go#L284

[webmaster128]

Thank you for bringing this up. I'm not sure if developing cosmwasm-vm on Windows is in scope. So far we only supported contract development on Windows. But even if we don't support development on Windows, we should be able to run the tests if we want to support libwasmvm on Windows.

The error message thing can be fixed one way or another. But not being able to use symlinks is bad. But it seems like this problem is solved: https://stackoverflow.com/questions/5917249/git-symbolic-links-in-windows/59761201#59761201

[webmaster128]

May I invite you to have a look at #1406 and check if this passes on Windows?

[webmaster128]

Created windows symlinks for wasm files as windows does not recognize linux symlinks.

#1499 shows a CI integration which enables symlinks on Windows. So we can just use them.