Test on multiple hosts

[mciantyre]

Ensure that all BSP examples build on macOS, Ubuntu, and Windows.

[mciantyre]

bors try

[bors[bot]]

try

Build succeeded:

• format
• template
• xplat (macos-latest)
• xplat (ubuntu-latest)
• xplat (windows-latest)
• precompiled
• test
• clippy
• doc

[mciantyre]

bors r+

[bors[bot]]

Build succeeded:

• clippy
• doc
• format
• precompiled
• template
• test
• xplat (macos-latest)
• xplat (ubuntu-latest)
• xplat (windows-latest)