AppVeyor CI: use build script for linux and MSBuild for Windows

Question

Scenario

I have a CMake project on AppVeyor that I am trying to add Linux Builds to. My Windows builds use a CMake generator in the before_build script to generate a visual studio solution which is built with build: project.

I want to perform my Linux builds with build_script: instead. However, when I add a build script to the matrix I get the error:

The build phase is set to "MSBuild" mode (default), but no Visual Studio project or solution files were found in the root directory. If you are not building Visual Studio project switch build mode to "Script" and provide your custom build command.

Attempted solutions

I have tried adding build: off and build: Script to the matrix however none of those options helped. Is my only option to define a script for Windows and use build_script on both platforms?

Example

My appveyor.yml file looks like this

version: 'build-{build}-{branch}'

image:
  - Visual Studio 2017
  - Ubuntu

platform:
  - x64

configuration:
  - Release
  - Debug

environment:
  APPVEYOR_YML_DISABLE_PS_LINUX: true

install:
  - ps: .\install-dependency.ps1
  - sh: ./install-dependency.sh

for:
-
  matrix:
    only:
      - image: Ubuntu
  before_build:
    - mkdir -p build; cd build; cmake -DCMAKE_BUILD_TYPE=%CONFIGURATION% ..
  build_script:
    - make

 -
   matrix:
     only:
       - image: Visual Studio 2017
   before_build:
     - cmake -G "Visual Studio 15 2017" -A x64 .
   build:
     project: $(APPVEYOR_PROJECT_NAME).sln

test_script:
  - CTest -C %CONFIGURATION%

---

Attempted solution details

For reference this is how I tried specifying the build options

matrix:
  only:
    - image: Ubuntu
build: Script
before_build:
  - mkdir -p build; cd build; cmake -DCMAKE_BUILD_TYPE=%CONFIGURATION% ..

---

Further Research

I tried performing a standalone Linux build, everything works as expected and I don't need to modify any script parameters. Maybe AppVeyor does not support mixing build types even with a matrix set up.

version: 'build-{build}-{branch}'

image: Ubuntu

platform:
  - x64

configuration:
  - Release
  - Debug

install:
  - sh: ./install-dependency.sh

before_build:
  - mkdir -p build; cd build; cmake -DCMAKE_BUILD_TYPE=%CONFIGURATION% ..

build_script:
  - make

test_script:
  - ctest -C %CONFIGURATION%

Answer 1

Although I have not found a solution to the question asked there is a workaround for building on both platforms. For Windows I can use the default MSBuild script msbuild <project> /logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll".

version: 'build-{build}-{branch}'

image:
  - Visual Studio 2017
  - Ubuntu

platform:
  - x64

configuration:
  - Release
  - Debug

environment:
  APPVEYOR_YML_DISABLE_PS_LINUX: true

install:
  - ps: .\install-dependency.ps1
  - sh: ./install-dependency.sh

for:
-
  matrix:
    only:
      - image: Ubuntu
  before_build:
    - mkdir -p build; cd build; cmake -DCMAKE_BUILD_TYPE=%CONFIGURATION% ..
  build_script:
    - make

 -
   matrix:
     only:
       - image: Visual Studio 2017
   before_build:
     - cmake -G "Visual Studio 15 2017" -A x64 .
  build_script:
    - msbuild %APPVEYOR_PROJECT_NAME%.sln /logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll"

test_script:
  - ctest -C %CONFIGURATION%