WIP: Don't link plugin dependencies to products

This doesn't look right, but a comment was changed when the code change was made, suggesting it was intentional.

Author: neonichu

Sources/Build/BuildPlan.swift

@@ -705,16 +705,16 @@ public class BuildPlan: SPMBuildCore.BuildPlan {
                 return target.dependencies.filter { $0.satisfies(self.buildEnvironment) }
 
             // For a product dependency, we only include its content only if we
-            // need to statically link it or if it's a plugin.
+            // need to statically link it.
             case .product(let product, _):
                 guard dependency.satisfies(self.buildEnvironment) else {
                     return []
                 }
 
                 switch product.type {
-                case .library(.automatic), .library(.static), .plugin:
+                case .library(.automatic), .library(.static):
                     return product.targets.map { .target($0, conditions: []) }
-                case .library(.dynamic), .test, .executable, .snippet, .macro:
+                case .library(.dynamic), .test, .executable, .snippet, .macro, .plugin:
                     return []
                 }
             }