Build with Boost 1.74

@gubatron You must add "cxxflags-frtti"
in all config files. Then the project compiles with 1.74 boost without errors.

frostwire-jlibtorrent/swig/config/android-arm64-config.jam

Line 11 in 00d14ca

<cxxflags>-fno-strict-aliasing

second bug:

frostwire-jlibtorrent/swig/config/android-arm-config.jam

    
           using clang-linux : arm : $(ANDROID_TOOLCHAIN)/bin/armv7a-linux-androideabi$(android_api)-clang++

you forgot to add ":"
and check all configs for these bugs.

And fix it in your script aldenml/libtorrent4j#155 (comment)

Restore it to the way it was before:

`prepare_android_toolchain() {
abort_if_var_unset "SRC" ${SRC}
abort_if_var_unset "NDK_VERSION" ${NDK_VERSION}
abort_if_var_unset "os_arch" ${os_arch}
abort_if_var_unset "android_api" ${android_api}
pushd ${SRC}

host_os="linux"
if [[ "$OSTYPE" == "darwin"* ]]; then
host_os="darwin"
fi

if [ ! -f android-ndk-${NDK_VERSION}.zip ]; then
prompt_msg "Downloading android-ndk-${NDK_VERSION}"
wget -4 -O android-ndk-${NDK_VERSION}.zip https://dl.google.com/android/repository/android-ndk-${NDK_VERSION}-${host_os}-x86_64.zip;
prompt_msg "Extracting NDK...wait";
unzip -qq android-ndk-${NDK_VERSION}.zip;
fi
NDK=$PWD/android-ndk-${NDK_VERSION};
prompt_msg "NDK=${NDK}"
TOOLCHAIN_FOLDER="android-toolchain-${os_arch}-api_${android_api}"
prompt_msg "Creating android toolchain --arch ${os_arch} --api ${android_api} --stl libc++ --install-dir ${TOOLCHAIN_FOLDER}"
python3 $NDK/build/tools/make_standalone_toolchain.py --arch ${os_arch} --api ${android_api} --stl libc++ --install-dir ${TOOLCHAIN_FOLDER};
ANDROID_TOOLCHAIN=${PWD}/${TOOLCHAIN_FOLDER}
#prompt_msg "Setting prebuilt ANDROID_TOOLCHAIN (arch ${os_arch}, api ${android_api})"
prompt_msg "ANDROID_TOOLCHAIN=${ANDROID_TOOLCHAIN}"
popd
}`

To support Android 19.

And I think we need to move away from using Travis. Travis is a paid service that requires money for compilation.
The compilation can be done for free, on the local computer.

@gubatron I win the game!
I was able to compile libtorrent version 1.2.12.0 with boost 1.75 and still keep compatibility with Android 4.4.
Before you start, erase everything you have in src.
The attached file is a 100% working swig. Fix your code with it.
swig.zip

And I used the local computer to compile, not Travis.

Beautiful initiative.

if you pay attention to my latest commits, Ive beeb making sure the local builds work, precisely because Travis Community is no more.

I'm only having issues now linking the android 32-bit libraries (both arm and 64bit)

I'll try some of what you've done here and include it on the local builds.

Once that's working, the plan is to the port the build scripts to create the artifacts using GitHub actions.

Will get back to you as I work more on this and take a closer look