bugfix: BuildTargetInfo for mill-build #11762

Job	Run time
windows-latest jdk-17 unit tests 1 / 2	18m 50s
windows-latest jdk-17 unit tests 2 / 2	16m 23s
Gradle MacOS integration	16m 1s
macOS-latest jdk-17 unit tests 1 / 2	24m 17s
Sbt integration	49m 24s
macOS-latest jdk-17 unit tests 2 / 2	35m 48s
Maven integration	6m 58s
ubuntu-latest jdk-17 unit tests 1 / 2	13m 51s
Gradle integration	7m 2s
ubuntu-latest jdk-17 unit tests 2 / 2	12m 41s
Scala CLI integration	10m 16s
ubuntu-latest jdk-8 unit tests 1 / 2	15m 51s
Mill integration	26m 11s
ubuntu-latest jdk-8 unit tests 2 / 2	24m 36s
LSP integration tests	25m 25s
Scala cross tests	45m 2s
Formatting	47s
Scalafix and docs	11m 41s
Sbt-metals/scripted jdk8	1m 40s
Scala javapc tests	2m 59s
Scala3 latest NIGHTLY cross test	4m 33s
MiMa	1m 10s
	6h 11m 26s

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