QemuPkg: building.md: Update instructions for using QEMU

[Javagedes]

Description

Updates the build instructions for using QEMU on windows and Linux to accurately specify that QEMU is provided automatically on Windows but should manually be downloaded on Linux. Additionally specifies that QEMU 9.0.2 or greater is necessary to boot the operating system on Linux.

Closes #1012

• [ ] Impacts functionality?
  • Functionality - Does the change ultimately impact how firmware functions?
  • Examples: Add a new library, publish a new PPI, update an algorithm, ...
• [ ] Impacts security?
  • Security - Does the change have a direct security impact on an application, flow, or firmware?
  • Examples: Crypto algorithm change, buffer overflow fix, parameter validation improvement, ...
• [ ] Breaking change?
  • Breaking change - Will anyone consuming this change experience a break in build or boot behavior?
  • Examples: Add a new library class, move a module to a different repo, call a function in a new library class in a pre-existing module, ...
• [ ] Includes tests?
  • Tests - Does the change include any explicit test code?
  • Examples: Unit tests, integration tests, robot tests, ...
• [x] Includes documentation?
  • Documentation - Does the change contain explicit documentation additions outside direct code modifications (and comments)?
  • Examples: Update readme file, add feature readme file, link to documentation on an a separate Web page, ...

How This Was Tested

N/A

Integration Instructions

N/A

[Javagedes]

test

Secondary effect of this, you reminded me I never merged it. Thanks :)