Add cmake CI test and fix pthread detection

.github/workflows/cmake-build.yml

@@ -0,0 +1,44 @@
+name: wolfMQTT CMake Build Tests
+
+on:
+  push:
+    branches: [ 'master', 'main', 'release/**' ]
+  pull_request:
+    branches: [ '*' ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+# Install cmake
+    - name: Install cmake
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y cmake
+
+#pull and build wolfssl
+    - uses: actions/checkout@master
+      with:
+        repository: wolfssl/wolfssl
+        path: wolfssl
+    - name: Build wolfssl
+      working-directory: ./wolfssl
+      run: |
+        mkdir build
+        cd build
+        cmake ..
+        cmake --build .
+        sudo cmake --install .
+
+#pull wolfMQTT
+    - uses: actions/checkout@master
+
+#build wolfMQTT
+    - name: Build wolfMQTT
+      run: |
+        mkdir build
+        cd build
+        cmake ..
+        cmake --build .

CMakeLists.txt

@@ -26,8 +26,6 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 
 include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/functions.cmake)
 
-find_package(Threads)
-
 set(MQTT_SOURCES
     src/mqtt_client.c
     src/mqtt_packet.c
@@ -147,6 +145,7 @@ add_option(WOLFMQTT_MT
            "no" "yes;no")
 if (WOLFMQTT_MT)
     list(APPEND WOLFMQTT_DEFINITIONS "-DWOLFMQTT_MULTITHREAD")
+    find_package(Threads REQUIRED)
 endif()
 
 add_option(WOLFMQTT_CURL
@@ -224,7 +223,11 @@ if (WOLFMQTT_EXAMPLES)
         examples/mqttexample.c
         examples/mqttnet.c
         )
-    target_link_libraries(mqtt_test_lib wolfmqtt)
+    if (WOLFMQTT_MT)
+        target_link_libraries(mqtt_test_lib wolfmqtt pthread)
+    else()
+        target_link_libraries(mqtt_test_lib wolfmqtt)
+    endif()
 
     function(add_mqtt_example name src)
         add_executable(${name}