GHA: use same flags for Slackbuild as Slack package

Closes #10526

.github/workflows/linux.yml

@@ -115,8 +115,10 @@ jobs:
           install_packages: clang libnss3-dev libnghttp2-dev nss-plugin-pem
           configure: CC=clang CPPFLAGS="-isystem /usr/include/nss" --with-nss --enable-debug --with-nss-deprecated
 
-        - name: Slackware-openssl-gcc
-          configure: --with-openssl
+        - name: Slackware-openssl-with-gssapi-gcc
+          # These are essentially the same flags used to build the curl Slackware package
+          # https://ftpmirror.infania.net/slackware/slackware64-current/source/n/curl/curl.SlackBuild
+          configure: --with-openssl --with-libssh2 --with-gssapi --enable-ares --enable-static=no --without-ca-bundle --with-ca-path=/etc/ssl/certs
           # Docker Hub image that `container-job` executes in
           container: 'andy5995/slackware-build-essential:15.0'