Python package generation generates invalid rpm specfile when there are spaces in a filename

[dwighthubbard]

Describe the bug

The briefcase package command fails with messages such as:

error: File must begin with "/": manifest.xml
error: File must begin with "/": (dev).tmpl

Lines matching the strings listed in the spec file contain a space character:

/usr/lib64/rpmtest/app_packages/setuptools/command/launcher manifest.xml
/usr/lib64/rpmtest/app_packages/setuptools/script (dev).tmpl

Steps to reproduce

In a Linux environment (reproduced on Almalinux 9)

1. Create a new project with briefcase new
2. Add redislite to the [tool.briefcase.app.rpmtest] requires
3. Create the Application using briefcase create
4. Build the project using briefcase build
5. Attempt to create an rpm package using briefcase package

Expected behavior

An rpm package gets created

Screenshots

No response

Environment

• Almalinux 9.1:
• Python version: 3.9.14
• Software versions:
  • Briefcase: 0.3.14

Logs

[briefcase.2023_04_25-20_43_53.package.log](https://github.com/beeware/briefcase/files/11326841/briefcase.2023_04_25-20_43_53.package.log)

Additional context

No response