travis: add a CI job with openssl3 (from git master)

Closes #5908

.travis.yml

@@ -152,6 +152,17 @@ jobs:
         - libpsl-dev
         - libbrotli-dev
         - libzstd-dev
+  - env:
+    - T=debug OPENSSL3="yes" C="--with-ssl=$HOME/openssl3" LD_LIBRARY_PATH=/home/travis/openssl3/lib:/usr/local/lib
+    - OVERRIDE_CC="CC=gcc-8" OVERRIDE_CXX="CXX=g++-8"
+    addons:
+      apt:
+        <<: *common_apt
+        packages:
+        - *common_packages
+        - libpsl-dev
+        - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=debug-mesalink C="--with-mesalink --without-ssl" MESALINK=yes
     - OVERRIDE_CC="CC=gcc-8" OVERRIDE_CXX="CXX=g++-8"

scripts/travis/before_script.sh

@@ -89,6 +89,15 @@ if [ "$TRAVIS_OS_NAME" = linux -a "$BORINGSSL" ]; then
   export LIBS=-lpthread
 fi
 
+if [ "$TRAVIS_OS_NAME" = linux -a "$OPENSSL3" ]; then
+  cd $HOME
+  git clone --depth=1 https://github.com/openssl/openssl
+  cd openssl
+  ./config enable-tls1_3 --prefix=$HOME/openssl3
+  make
+  make install_sw
+fi
+
 if [ "$TRAVIS_OS_NAME" = linux -a "$QUICHE" ]; then
   cd $HOME
   git clone --depth=1 --recursive https://github.com/cloudflare/quiche.git