Update CI to use sufficiently new versions of Flutter

Author: stuartmorgan-g

.appveyor.yml

@@ -17,7 +17,10 @@ image: Visual Studio 2017
 platform: x64
 
 install:
-  - ps: build\ci\install_flutter.ps1 $env:APPVEYOR_BUILD_FOLDER\..
+  # None of the packaged channels are new enough for the current state
+  # of FDE, so for now clone master instead.
+  #- ps: build\ci\install_flutter.ps1 $env:APPVEYOR_BUILD_FOLDER\..
+  - git clone -b master https://github.com/flutter/flutter.git
 
 build_script:
   - msbuild "example\windows_fde\Example Embedder.sln"

build/ci/install_flutter

@@ -16,8 +16,8 @@
 
 set -e
 
-readonly CHANNEL="stable"
-readonly VERSION="1.0.0"
+readonly CHANNEL="dev"
+readonly VERSION="1.1.8"
 
 if [[ "${TRAVIS_OS_NAME}" == "linux" ]]; then
   readonly FLUTTER_OS="linux"