Link the updater with OpenSSL explicitely, only link Aria2 with OpenSSL as crypto library

[illwieckz]

• Link the updater with OpenSSL explicitely

On my end, outside of Docker, I need those linker flags.

• Only link Aria2 with OpenSSL as crypto library

Useful instructions in the README to avoid linking with many crypto libraries in our back.
Does the same in Docker just in case.

[slipher]

For the updater release build, we don't want -lssl -lcrypto because we want to statically link OpenSSL into aria2/Qt. This should cause an error in the Docker build because we don't provide the location of SSL libs when building the updater, though it might slip by if the host system happens to have the SSL solibs installed.

I'm working on Qt6+CMake migration and in the CMakeLists.txt I added an ARIA2_LIBS configuration option to give us a bit more flexibility there. Not sure how to backport it to qmake. In the meantime a workaround is to build aria2 as shared instead of static as we do in the CI script.

[illwieckz]

OK.

I'm working on Qt6+CMake migration.

Great!

[slipher]

Turns out this actually happens automatically with Qt6 + CMake. When you find the Qt6::Network library, it automatically searches for its "WrapOpenSSL" target as a required dependency.

[illwieckz]

Now unneeded.