Use default cpp fmt build script.

vendor/Fmt/support/build.gradle

@@ -0,0 +1,132 @@
+import java.nio.file.Paths
+
+// General gradle arguments for root project
+buildscript {    
+    repositories {
+        google()
+        jcenter()
+    }
+    dependencies {
+        //
+        // https://developer.android.com/studio/releases/gradle-plugin#updating-gradle
+        //
+        // Notice that 4.0.0 here is the version of [Android Gradle Plugin]
+        // Accroding to URL above you will need Gradle 6.1 or higher
+        //
+        classpath "com.android.tools.build:gradle:4.1.1"
+    }
+}
+repositories {
+    google()
+    jcenter()
+}
+
+// Project's root where CMakeLists.txt exists: rootDir/support/.cxx -> rootDir
+def rootDir = Paths.get(project.buildDir.getParent()).getParent()
+println("rootDir: ${rootDir}")
+
+// Output: Shared library (.so) for Android 
+apply plugin: "com.android.library"
+android {
+    compileSdkVersion 25    // Android 7.0
+
+    // Target ABI
+    //  - This option controls target platform of module
+    //  - The platform might be limited by compiler's support
+    //    some can work with Clang(default), but some can work only with GCC...
+    //    if bad, both toolchains might not support it
+    splits {
+        abi {
+            enable true
+            // Specify platforms for Application
+            reset()
+            include  "arm64-v8a", "armeabi-v7a", "x86_64"
+        }
+    }
+    ndkVersion "21.3.6528147" // ANDROID_NDK_HOME is deprecated. Be explicit
+
+    defaultConfig {
+        minSdkVersion 21    // Android 5.0+
+        targetSdkVersion 25 // Follow Compile SDK
+        versionCode 34      // Follow release count
+        versionName "7.1.2" // Follow Official version
+        
+        externalNativeBuild {
+            cmake {
+                arguments "-DANDROID_STL=c++_shared"    // Specify Android STL
+                arguments "-DBUILD_SHARED_LIBS=true"    // Build shared object
+                arguments "-DFMT_TEST=false"            // Skip test
+                arguments "-DFMT_DOC=false"             // Skip document
+                cppFlags  "-std=c++17"
+                targets   "fmt"
+            }
+        }
+        println(externalNativeBuild.cmake.cppFlags)
+        println(externalNativeBuild.cmake.arguments)
+    }
+
+    // External Native build
+    //  - Use existing CMakeList.txt
+    //  - Give path to CMake. This gradle file should be 
+    //    neighbor of the top level cmake
+    externalNativeBuild {
+        cmake {
+            version "3.10.0+"
+            path "${rootDir}/CMakeLists.txt"
+            // buildStagingDirectory "./build"  // Custom path for cmake output
+        }
+    }
+    
+    sourceSets{
+        // Android Manifest for Gradle
+        main {
+            manifest.srcFile "AndroidManifest.xml"
+        }
+    }
+
+    // https://developer.android.com/studio/build/native-dependencies#build_system_configuration
+    buildFeatures {
+        prefab true
+        prefabPublishing true
+    }
+    prefab {
+        fmt {
+            headers "${rootDir}/include"
+        }
+    }
+}
+
+assemble.doLast
+{
+    // Instead of `ninja install`, Gradle will deploy the files.
+    // We are doing this since FMT is dependent to the ANDROID_STL after build
+    copy {
+        from "build/intermediates/cmake"
+        into "${rootDir}/libs"
+    }
+    // Copy debug binaries
+    copy {
+        from "${rootDir}/libs/debug/obj"
+        into "${rootDir}/libs/debug"
+    }
+    // Copy Release binaries
+    copy {
+        from "${rootDir}/libs/release/obj"
+        into "${rootDir}/libs/release"
+    }
+    // Remove empty directory
+    delete "${rootDir}/libs/debug/obj"
+    delete "${rootDir}/libs/release/obj"
+
+    // Copy AAR files. Notice that the aar is named after the folder of this script.
+    copy {
+        from "build/outputs/aar/support-release.aar"
+        into "${rootDir}/libs"
+        rename "support-release.aar", "fmt-release.aar"
+    }
+    copy {
+        from "build/outputs/aar/support-debug.aar"
+        into "${rootDir}/libs"
+        rename "support-debug.aar", "fmt-debug.aar"
+    }
+}