Previously, the classpath of bootJar, bootWar, and bootRun was
configured directly as a FileCollection derived from the main source
set's runtime classpath. This direct configuration meant that
subsequent changes to the main source set's runtime classpath may not
have been picked up.
This commit changes the configuration of the classpath to use a
Callable. This indirection allows subsequent changes to the main
source set's runtime classpath to be picked up as long as they
occur before Gradle calls the callable.
Closes gh-29672
43ca2d2cb0