| <p><code>List of <a href="${link build-ref#labels}">labels</a> |
| ; optional; |
| <a href="#configurable-attributes">nonconfigurable</a></code> |
| </p> |
| |
| <p> |
| A list of |
| <code><a href="platform.html#constraint_value">constraint_values</a></code> |
| that must be present in the execution platform for this target. This is in |
| addition to any constraints already set by the rule type. Constraints are used |
| to restrict the list of available execution platforms. For more details, see |
| the description of |
| <a href="/docs/toolchains#toolchain-resolution">toolchain resolution</a>. |
| </p> |