message: [appveyor] Install yasm if gRPC++ isn't disabled
  The previous approach only installed yasm for entries in the matrix that
  explicitly opted-in, which resulted in duplicate state. Now, it figures
  out whether yasm is needed by looking for the BOND_ENABLE_GRPC CMake
  flag.
diff: BOND_VS_NUM: 14
  BOND_ARCH: 64
  BOND_BOOST: 63
  - BOND_GRPC: "true"
  BOND_CMAKE_FLAGS: "-DBOND_ENABLE_COMM=FALSE;-DBOND_SKIP_CORE_TESTS=TRUE;-DBOND_SKIP_GBC_TESTS=TRUE"
  - BOND_BUILD: C#
  BOND_OUTPUT: Properties
  }
  - if ($env:BOND_GRPC -eq "true") {
  + if (($env:BOND_BUILD -eq 'C++') -and (-not ($env:BOND_CMAKE_FLAGS -match '-DBOND_ENABLE_GRPC=FALSE'))) {
  +
  + # We're building C++ and gRPC isn't disabled, so we need
  + # gRPC dependencies.
  choco install yasm -y
  + $machinePath = [System.Environment]::GetEnvironmentVariable("Path","Machine")
  +
  + $userPath = [System.Environment]::GetEnvironmentVariable("Path","User")
  +
  + $env:Path = "$machinePath;$userPath"
  +
  }
  cache:
  