Update top-level javadoc

Gradle 9 is pretty strict about enforcing its concurrency model,
which tripped up our consolidated javadoc generation. This updates
that so that we are explicitly depending on each subproject
in the javadoc task and adding the classpath files as an input.

Author: JordonPhillips

build.gradle.kts

@@ -44,8 +44,18 @@ afterEvaluate {
         javadoc {
             title = "Smithy API ${version}"
             setDestinationDir(layout.buildDirectory.dir("docs/javadoc/latest").get().asFile)
-            source(subprojects.map { project(it.path).sourceSets.main.get().allJava })
-            classpath = files(subprojects.map { project(it.path).sourceSets.main.get().compileClasspath })
+
+            // Add an explicit dependencies on the compilation of each subproject because we need
+            // the compile classpath, which we can only get after the compile task has completed.
+            dependsOn(subprojects.map { it.tasks.named("compileJava") })
+            classpath = files(provider {
+                subprojects.flatMap { subproject ->
+                    subproject.configurations.getByName("compileClasspath").resolve()
+                }
+            })
+
+            source(provider { subprojects.map { project -> project.sourceSets.main.get().allJava } })
+
             (options as StandardJavadocDocletOptions).apply {
                 addStringOption("Xdoclint:-html", "-quiet")
             }