Repository: go
Issue: x/tools/go/loader: TestLoad_MissingInitialPackage failures on LUCI `wasip1` builders with EBADF errors
Labels: NeedsInvestigation,arch-wasm,Tools

```
#!watchflakes
post <- goos == "wasip1" && pkg == "golang.org/x/tools/go/loader" && test == "TestLoad_MissingInitialPackage" && `Bad file number`
```

### Go version

N/A

### What operating system and processor architecture are you using (`go env`)?

```shell
N/A
```


### What did you do?

Check LUCI build status for `x/tools`:
https://ci.chromium.org/p/golang/g/x-tools-gotip/console

### What did you expect to see?

All tests passing.

### What did you see instead?

A recurring pattern of failures:
```
=== RUN   TestLoad_MissingInitialPackage
read /home/swarming/.swarming/w/ir/x/w/goroot/src/internal/abi/switch.go: Bad file number
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:427:24: undefined: abi.TypeAssert
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:467:37: undefined: abi.TypeAssertCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:467:82: undefined: abi.TypeAssertCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:514:32: undefined: abi.TypeAssertCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:521:29: undefined: abi.InterfaceSwitch
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:573:42: undefined: abi.InterfaceSwitchCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:573:103: undefined: abi.InterfaceSwitchCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:621:37: undefined: abi.InterfaceSwitchCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:437:10: undefined: abi.UseInterfaceSwitchCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:448:16: undefined: abi.TypeAssertCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:485:31: undefined: abi.TypeAssertCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:485:86: undefined: abi.TypeAssertCacheEntry
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:486:16: undefined: abi.TypeAssertCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:537:10: undefined: abi.UseInterfaceSwitchCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:550:16: undefined: abi.InterfaceSwitchCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:591:31: undefined: abi.InterfaceSwitchCache
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:591:91: undefined: abi.InterfaceSwitchCacheEntry
/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/iface.go:592:16: undefined: abi.InterfaceSwitchCache
go/build: go list nosuchpkg: pipe: Not implemented on wasip1


    loader_test.go:131: Load failed with wrong error "couldn't load packages due to errors: nosuchpkg, internal/abi, runtime", want "couldn't load packages due to errors: nosuchpkg"
--- FAIL: TestLoad_MissingInitialPackage (10.43s)
```

- http://ci.chromium.org/b/8761791908815708145/test-results
- http://ci.chromium.org/b/8761792115662016017/test-results
- http://ci.chromium.org/b/8761884870840140577/test-results

(attn @golang/wasm)