Reuse webMain instead of recreating it

Kotlin 2.2’s default hierarchy creates `webMain` when both JS and WASM
targets are present. Re-creating it manually fails with the error
“KotlinSourceSet with name 'webMain' already exists”.

Author: goncalossilva

buildSrc/src/main/kotlin/targets.gradle.kts

@@ -70,15 +70,7 @@ fun KotlinMultiplatformExtension.configureCommonTargets() {
     }
 
     sourceSets {
-        val webMain by creating {
-            dependsOn(commonMain.get())
-        }
-        jsMain {
-            dependsOn(webMain)
-        }
-        wasmJsMain {
-            dependsOn(webMain)
-        }
+        val webMain by getting
 
         jvmTest.dependencies {
             implementation(kotlin("test-junit"))