Okay so .appveyor.yml cmd scripts must not have multiline commands, ugh.

.appveyor.yml

@@ -36,14 +36,12 @@ environment:
 platform:
   - x64
 
-before_build:
+# Note: AppVeyor tries to be "helpful" and splits cmd.exe scripts into their constitutent lines to check their error codes. There is no way to switch this off; for true multi-line scripts we have to use PowerShell. But we need to use vcvarsall.bat, so that's out of the question.
+install:
   - cmd: |
       rem Set Python Version
-      if %arch%==386 (
-        set PYTHON_ROOT=C:\python37
-      ) else (
-        set PYTHON_ROOT=C:\python37-x64
-      )
+      set PYTHON_ROOT=C:\python37-x64
+      if %arch%==386 ( set PYTHON_ROOT=C:\python37 )
       set "PATH=%PYTHON_ROOT%;%PYTHON_ROOT%\Scripts;%PATH%"
       
       rem Install Latest Meson
@@ -54,45 +52,35 @@ before_build:
       mkdir C:\ninja
       powershell -Command "Expand-Archive -LiteralPath C:\ninja-win.zip -DestinationPath C:\ninja"
       set "PATH=C:\ninja;%PATH%"
+      
+      rem Parameters for the build_script phase, to reduce their noise.
+      set "mingwPath=C:\msys64\mingw64\bin"
+      set vcvarsallArch=x86
+      if %arch%==386 ( set "mingwPath=C:\msys64\mingw32\bin" )
+      if %arch%==386 ( set vcvarsallArch=amd64 )
 
 build_script:
   - cmd: |
-      if %compiler%==mingw-Win32 (
-        if %arch%==386 (
-          set "PATH=C:\msys64\mingw32\bin;%PATH%"
-        ) else (
-          set "PATH=C:\msys64\mingw64\bin;%PATH%"
-        )
-      ) else (
-        if %arch%==386 (
-          call "C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat" x86
-        ) else (
-          call "C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat" amd64
-        )
-      )
+      if %compiler%==mingw ( set "PATH=%mingwPath%;%PATH%" )
+      if %compiler%<>mingw ( call "C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat" %vcvarsallArch% )
       meson setup build --buildtype=release --default-library=%libtype%
       ninja -C build
 
 after_build:
   - cmd: |
-      if %APPVEYOR_REPO_TAG%==true (
-        set "version=%APPVEYOR_REPO_TAG_NAME%"
-      ) else (
-        set "version=%APPVEYOR_REPO_BRANCH%"
-      )
+      set "version=%APPVEYOR_REPO_BRANCH%"
+      if %APPVEYOR_REPO_TAG%==true ( set "version=%APPVEYOR_REPO_TAG_NAME%" )
       set "artifact=%version%-windows-%arch%-%compiler%-%libtype%"
       pushd build\meson-out
-      if %buildtype%==static (
-        rem TODO msvc only?
-        ren libui.a libui.lib
-      )
+      rem TODO msvc only?
+      if %buildtype%==static ( ren libui.a libui.lib )
       copy ..\..\ui.h .
       copy ..\..\ui_windows.h .
       rem remove unnecessary files
       rem TODO should we do this on Azure too?
       del libui.exp
       7z a "%APPVEYOR_BUILD_FOLDER%\libui-%artifact%.zip" %libfiles% ui.h ui_windows.h
-      7z a "%APPVEYOR_BUILD_FOLDER%\examples-%artifact%.zip" *.exe
+      7z a "%APPVEYOR_BUILD_FOLDER%\examples-%artifact%.zip" controlgallery.exe cpp-multithread.exe datetime.exe drawtext.exe histogram.exe tester.exe timer.exe
       popd
 
 artifacts: