Hack to make x86-64 work with Android NDK-25

The new NDK doesn't link to `libgcc`, which breaks our our NSS and
SQLCipher libraries since they depended on the symbols from
libclang_rt.builtins-x86_64-android` like `__extenddftf2`. See mozilla#5436 for
more details.

The hack works around this by taking object files from the built
libraries and `libclang_rt.builtins-x86_64-android.a`, and combining
them together to get the final static library.

libs/build-all-android.sh

@@ -46,3 +46,23 @@ for i in "${!TARGET_ARCHS[@]}"; do
     ./build-sqlcipher-android.sh "${SQLCIPHER_SRC_PATH}" "${DIST_DIR}" "${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/${NDK_HOST_TAG}" "${TARGET_ARCHS_TOOLCHAINS[${i}]}" "${ANDROID_NDK_API_VERSION}" "${NSS_DIR}" || exit 1
   fi
 done
+
+echo "# Adding missing X86-64 compiler builtins"
+add_missing_x86_64_symbols() {
+  LIBRARY=$1
+  shift
+  # after shift, the extra libraries are in $@
+  AR="${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/${NDK_HOST_TAG}/bin/llvm-ar"
+  WORKDIR=$(mktemp -d)
+  pushd $WORKDIR
+  # Extract all object files from the library
+  $AR x $LIBRARY
+  # Extract the object files we need from libclang_rt.builtins-x86_64-android.a
+  $AR x "${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/${NDK_HOST_TAG}/lib64/clang/14.0.7/lib/linux/libclang_rt.builtins-x86_64-android.a" "$@"
+  # Create a new static lib with each extracted object file and use it
+  $AR cr fixed-lib.a *.o
+  mv fixed-lib.a $LIBRARY
+  popd
+}
+add_missing_x86_64_symbols $(abspath "android/x86_64/nss/lib/libnspr4.a") extenddftf2.c.o
+add_missing_x86_64_symbols $(abspath "android/x86_64/sqlcipher/lib/libsqlcipher.a") extenddftf2.c.o trunctfdf2.c.o multf3.c.o addtf3.c.o divtf3.c.o fixtfsi.c.o fp_mode.c.o floatditf.c.o floatsitf.c.o subtf3.c.o comparetf2.c.o