Download OpenSSL from Conan

[annulen]

Right now we download OpenSSL with qt-downloader, and it turned out to have 2 major issues:

• MSVC binaries are built with VS2010 (!) and require its runtime which is not preinstalled on Win10
• MinGW is shipped with OpenSSL 1.0.2 which is incompatible with Qt
  Also, qt.io doesn't update OpenSSL often (though our use case is not security-sensitive)

Alternative is to use Conan package. For example, to download OpenSSL built with VS2019 x86_64 following command can be used:

conan install 'openssl/[>=1.1.1g <3.0]@' -g deploy -o openssl:shared=True -s compiler="Visual Studio" -s os=Windows -s arch=x86_64 -s compiler.version=16

It creates openssl directory which contains necessary dlls in bin. Same can be used for x86. MinGW won't work out of the box so let's start from MSVC x86 and x86_64.

[annulen]

Now we have mingw too. Run

conan remote add qtproject https://api.bintray.com/conan/qtproject/conan --insert --force

and then one of the following commands:

# VS2019 x86
conan install 'openssl/[>=1.1.1g <3.0]@qtproject/stable' -g deploy -o openssl:shared=True -s compiler="Visual Studio" -s os=Windows -s arch=x86 -s compiler.version=16
# VS2019 x86_64
conan install 'openssl/[>=1.1.1g <3.0]@qtproject/stable' -g deploy -o openssl:shared=True -s compiler="Visual Studio" -s os=Windows -s arch=x86_64 -s compiler.version=16
# MinGW x86
conan install 'openssl/[>=1.1.1g <3.0]@qtproject/stable' -g deploy -o openssl:shared=True -s compiler=gcc -s os=Windows -s arch=x86 -s compiler.version=8 -s compiler.libcxx=libstdc++ -s compiler.exception=dwarf2 -s compiler.threads=posix
# MinGW x86_64
conan install 'openssl/[>=1.1.1g <3.0]@qtproject/stable' -g deploy -o openssl:shared=True -s compiler=gcc -s os=Windows -s arch=x86_64 -s compiler.version=8 -s compiler.libcxx=libstdc++ -s compiler.exception=seh -s compiler.threads=posix

to download one of packages.

[annulen]

I think we need a script "download-openssl" which gets following arguments: compiler (mingw/msvc), version (16 or 8 in this case), arch, output dir (goes to --install-folder of conan)