Build: Allow configuration of build matrix for the buildAll mage target

[marefr]

What would you like to be added:
Disable certain architecture/platform in the buildAll mage target.

Why is this needed:
In case a plugin can't be built on certain platform it would be helpful to be able to disable a certain architecture/platform without having to define your own custom build target for your plugin.

Example: The grafana-flightsql-datasource can't be built for Linux ARM since Arrow dependency isn't supported there so they've created there own build target, see https://github.com/influxdata/grafana-flightsql-datasource/blob/7372d9f646691ccd44f31347f53170c7c93876b4/Magefile.go#L12-L18. When the buildAll mage target was changed to also include the dependency of GenerateManifestFile the grafana-flightsql-datasource didn't get this update when upgrading the grafana-plugin-sdk-go. Same problem could arise if we introduce new architecture/platform to the build matrix.