Command Line Arguments:
/p:SetConnectionString="Data Source=(test);Initial Catalog=test;Persist Security Info=True;MultipleActiveResultSets=True" /t:Rebuild /property:Name=Test;CnStr=Custom 

runs as:
"C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\MSBuild\15.0\Bin\msbuild.exe" /nr:false "/p:SetConnectionString=Data Source=(test);Initial Catalog=test;Persist Security Info=True;MultipleActiveResultSets=True" /t:Rebuild /property:Name=Test;CnStr=Custom build_script.xml

Value of SetConnectionString param and any other value that contains ';' becomes unuseful