Merge branch 'kotlin-missing-lib-fix'

bindings/kotlin/.gitignore

@@ -4,4 +4,5 @@
 # Ignore Gradle build output directory
 build
 
+local.properties
 *.hprof

bindings/kotlin/lib/build.gradle

@@ -7,6 +7,7 @@ plugins {
 
 android {
     compileSdkVersion 33
+
     ndkVersion '25.2.9519653'
 
     namespace 'org.equalitie.ouisync'
@@ -64,10 +65,29 @@ dependencies {
 cargo {
     module = "$rootDir/../.."
     libname = 'ouisync_ffi'
+
+    // Targets can be overriden with "rust.targets" in local.properties.
+    // Example: "rust.targets=arm64,x86_64".
+    // More info: https://github.com/mozilla/rust-android-gradle.
     targets = ['arm', 'arm64', /* 'x86', */ 'x86_64']
+
     profile = 'release'
 
     extraCargoBuildArguments = ['--package', 'ouisync-ffi']
+
+    // HACK: Recent NDK (since r23) no longer links `libgcc`, which breaks some libraries since
+    // they depended on the symbols from `libclang_rt.builtins-x86_64-android`
+    // (e.g. `__extenddftf2`, ...). To work around it, we link the library explicitly by setting
+    // it through the RUSTFLAGS env variable.
+    // More info: https://github.com/bbqsrc/cargo-ndk/issues/94.
+    exec { spec, toolchain ->
+        if (toolchain.target == 'x86_64-linux-android') {
+            def clangVersion = '14.0.7'
+            def libDir = "${android.sdkDirectory}/ndk/${android.ndkVersion}/toolchains/llvm/prebuilt/linux-x86_64/lib64/clang/${clangVersion}/lib/linux"
+
+            spec.environment('RUSTFLAGS', "-L${libDir} -lstatic=clang_rt.builtins-x86_64-android")
+        }
+    }
 }
 
 tasks.register('generateBindings', Exec) {