CI: Add mbedTLS dependency for AppVeyor Linux

On Ubuntu 16.04 (Xenial), we have to build mbedTLS from source because
the version available from apt, mbedTLS 2.2.1, does not work with the
RTMPS implementation in OBS, which requires mbedTLS 2.7 at minimum. This
is due to the use of the function mbedtls_ssl_conf_dh_param_bin, which
was introduced in mbedTLS 2.7.

CI/install-dependencies-linux-ubuntu16.sh

@@ -38,3 +38,20 @@ sudo apt-get install -y \
         python3-dev \
         qtbase5-dev \
         swig
+
+
+# build mbedTLS
+cd ~/projects
+mkdir mbedtls
+cd mbedtls
+mbedtlsPath=$PWD
+curl -L -O https://github.com/ARMmbed/mbedtls/archive/mbedtls-2.12.0.tar.gz
+tar -xf mbedtls-2.12.0.tar.gz
+mkdir build
+cd ./build
+cmake -DENABLE_TESTING=Off -DUSE_SHARED_MBEDTLS_LIBRARY=On ../mbedtls-mbedtls-2.12.0
+make -j 12
+sudo make install
+
+# return to OBS build dir
+cd $APPVEYOR_BUILD_FOLDER