build: enable -Xstring-concat=inline for kotlin compilation

app/proguard-rules.pro

@@ -126,4 +126,4 @@
 ## Contributor models - deserialized with GSON
 -keep class * implements com.itsaky.androidide.contributors.Contributor {
   *;
-}
+}

build.gradle.kts

@@ -73,7 +73,10 @@ subprojects {
   }
 
   tasks.withType<KotlinCompile>().configureEach {
-    kotlinOptions.jvmTarget = BuildConfig.javaVersion.toString()
+    kotlinOptions {
+      jvmTarget = BuildConfig.javaVersion.toString()
+      freeCompilerArgs += "-Xstring-concat=inline"
+    }
   }
 }