NOTE: this problem only occurs when building using -buildmode=c-shared

Here is my reproducible setup:

export TMPDIR=/tmp
export HOME=/usr/local/google/home/$USER

$ mkdir -p $HOME/gotest/src/test
$ cat > $HOME/gotest/src/test/test.go
package main

import "C"

//export exportedFunc
func exportedFunc() {}

func main() {}

$ GOPATH=$HOME/gotest go install -buildmode=c-shared test

$ cat > $HOME/gotest/src/test/test.go
package main

import "C"

//export exportedFunc
func exportedFunc() {}

func main() {
}

$ GOPATH=$HOME/gotest go install -buildmode=c-shared -x test
....
cp $WORK/test/_obj/_cgo_install.h /usr/local/google/home/spetrovic/gotest/pkg/linux_amd64_shared/test.h
build output "/usr/local/google/home/spetrovic/gotest/pkg/linux_amd64_shared/test.h" already exists and is not an object file

The problem is that $WORK and $HOME are on different devices in my setup, and hence the os.Rename() fails to move the file _cgo_install.h with: "invalid cross-device link"; cmd/go/build.go then tries to copy the file over, but this code causes it to fail as well:

if !isObject(dst) {
return fmt.Errorf("build output %q already exists and is not an object file", dst)
}

My question is, what is the purpose of this isObject() check and can we get rid of it?