build: support 16KB page size and bump minSdkVersion to 21 (#604)

Author: jyyi1

Android/app/build.gradle

@@ -127,8 +127,8 @@ dependencies {
     // For Firebase Analytics, etc.
     implementation 'com.google.firebase:firebase-analytics:19.0.2'  // Last version for API <19
     implementation 'com.google.firebase:firebase-perf:20.0.4'
-    implementation 'com.google.firebase:firebase-crashlytics:18.2.6'
-    implementation 'com.google.firebase:firebase-crashlytics-ndk:18.2.6'
+    implementation 'com.google.firebase:firebase-crashlytics:19.0.2'
+    implementation 'com.google.firebase:firebase-crashlytics-ndk:19.0.2'
     implementation 'com.google.firebase:firebase-config:21.0.1'
 
     // Go backend (use fileTree instead of files to prevent Android Studio sync errors)
@@ -157,7 +157,12 @@ tasks.register('compileGoBackend', Exec) {
                         System.getenv('PATH')
 
     commandLine("${goBuildDir}/gomobile", 'bind',
-                '-ldflags=-s -w',
+                // -s -w: Omit symbol table and debug info to reduce binary size.
+                // -extldflags: Pass flags to the external linker (e.g., Clang):
+                //   * -Wl: Pass the subsequent option to the linker.
+                //   * -z: Pass a keyword option to the linker.
+                //   * max-page-size=16384: Align ELF to 16KB page for Android 15+.
+                '-ldflags=-s -w -extldflags=-Wl,-z,max-page-size=16384',
                 '-target=android',
                 "-androidapi=${android.defaultConfig.minSdk}",
                 '-o', goBackendAAR,

Android/gradle.properties

@@ -30,5 +30,5 @@ android.nonFinalResIds=false
 ANDROID_COMPILE_SDK_VERSION=35
 ANDROID_BUILD_TOOLS_VERSION=35.0.0
 
-ANDROID_MIN_SDK_VERSION=16
+ANDROID_MIN_SDK_VERSION=21
 ANDROID_TARGET_SDK_VERSION=35