Invoke build tool plugins based on allTargets (#6776)

Currently, we're only invoking build tool plugins for reachable targets which does not seem correct based on the fact that we're willing to build targets out of reachable, e.g. when executing a command plugin.

rdar://113264168

Author: neonichu

Sources/SPMBuildCore/PluginInvocation.swift

@@ -338,7 +338,7 @@ extension PackageGraph {
         builtToolHandler: (_ name: String, _ path: RelativePath) throws -> AbsolutePath? = { _, _ in return nil }
     ) throws -> [ResolvedTarget: [BuildToolPluginInvocationResult]] {
         var pluginResultsByTarget: [ResolvedTarget: [BuildToolPluginInvocationResult]] = [:]
-        for target in self.reachableTargets.sorted(by: { $0.name < $1.name }) {
+        for target in self.allTargets.sorted(by: { $0.name < $1.name }) {
             // Infer plugins from the declared dependencies, and collect them as well as any regular dependencies. Although usage of build tool plugins is declared separately from dependencies in the manifest, in the internal model we currently consider both to be dependencies.
             var pluginTargets: [PluginTarget] = []
             var dependencyTargets: [Target] = []