Enable macOS on appveyor

Author: ltjax

Diff for: .appveyor/install.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+set -e
+set -x
+
+if [[ "$(uname -s)" == 'Darwin' ]]; then
+    source ~/venv3.8.1/bin/activate
+    python --version
+
+    pip install conan --upgrade
+    pip install conan_package_tools
+    conan --version
+    conan user
+    conan config install conan_config/
+fi

Diff for: .appveyor/run.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+set -e
+set -x
+
+if [[ "$(uname -s)" == 'Darwin' ]]; then
+    source ~/venv3.8.1/bin/activate
+    python build.py
+fi

Diff for: appveyor.yml

@@ -10,16 +10,26 @@ environment:
     CONAN_UPLOAD: "https://api.bintray.com/conan/ltjax/conan"
 
     matrix:
+        - APPVEYOR_BUILD_WORKER_IMAGE: macos
+          CONAN_APPLE_CLANG_VERSIONS: "11.0"
         - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
           CONAN_VISUAL_VERSIONS: 16
         - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
           CONAN_VISUAL_VERSIONS: 15
 
 install:
-  - set PATH=%PATH%;%PYTHON%/Scripts/
-  - pip.exe install conan --upgrade
-  - pip.exe install conan_package_tools
-  - conan user # It creates the conan data directory
+  # Windows build
+  - cmd: set PATH=%PATH%;%PYTHON%/Scripts/
+  - cmd: pip.exe install conan --upgrade
+  - cmd: pip.exe install conan_package_tools
+  - cmd: conan user # It creates the conan data directory
+  # macOS build
+  - sh: chmod +x .appveyor/install.sh
+  - sh: .appveyor/install.sh
 
 test_script:
-  - python build.py
+  # Windows build
+  - cmd: python build.py
+  # macOS build
+  - sh: chmod +x .appveyor/run.sh
+  - sh: .appveyor/run.sh