fix: Add root build.gradle for clean task

Author: kjunh972

build.gradle

@@ -0,0 +1,10 @@
+plugins {
+    id 'base'
+}
+
+clean {
+    delete 'build'
+    delete fileTree(dir: '.') {
+        include '**/*.class'
+    }
+}

settings.gradle

@@ -1 +1,2 @@
-rootProject.name = 'Location-based-target-authentication'
+rootProject.name = 'BE'
+include 'Location-based-target-authentication'