File provisioner silently fails to upload file unless -debug flag is used

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#### Overview of the Issue

[This is my packerfile and cloud-config](https://gist.github.com/v1nsai/b454894fc4d443e369248f94ed8e4056)
Running this without debug results in silent failure of the file provisioner to upload the files correctly. This also prevents the `write_files` module of `cloudinit` from running.

Changing nothing other than adding the `-debug` flag causes file provisioner and cloudinit files to be written correctly.

#### Reproduction Steps
Running the above files using `packer build .` results in files either not being written to the disk image or blank files get written. Running `packer -debug build .` on the same directory and code results in both the file provisioner file and cloud-init file being written correctly.

### Packer version

From Packer v1.9.1

### Simplified Packer Template

[Link to gist containing packerfile + cloud-config files](https://gist.github.com/v1nsai/b454894fc4d443e369248f94ed8e4056)

### Operating system and Environment details

MacOS 13.3.1 MacBook Air 2020 Apple M1 CPU, 8GB RAM

### Log Fragments and crash.log files

No obvious errors, but this line looks strange. There's a nonzero stderr reported by SCP but no error info and build finishes successfully. Possibly relevant?

`2023/06/24 19:19:22 packer-plugin-qemu_v1.0.9_x5.0_darwin_arm64 plugin: 2023/06/24 19:19:22 [DEBUG] scp stderr (length 79): Sink: C0644 3829 provisioner-install.sh`