defaultplatform does not work with gmake

[ghost]

Hello,
in my project I'm using following code to set default platform based on OS type:

if os.is64bit() then
    defaultplatform "x86_64"
else
    defaultplatform "x86"
end

When used with Visual Studio target (eg. vs2017), this correctly sets default platform based on OS type. However, with gmake target the default platform always remains x86. This happens on both Linux and Windows.