Took new approach towards 'ARDUINO_SDK_PATH'.

To set it to a custom location, an environment variable must be defined.
Also removed email notifications, again, as they require specific mails.

Author: MrPointer

appveyor.yml

@@ -1,8 +1,5 @@
 version: '{build}'
 image: Visual Studio 2017
-notifications:
-- provider: Email
-  on_build_success: false
 environment:
   matrix:
   - ARDUINO_SDK_VERSION: 1.6.13

cmake/Arduino-Toolchain.cmake

@@ -31,13 +31,13 @@ endfunction()
 
 function(_setup_sdk_internal_paths)
 
-    set(ARDUINO_SDK_BIN_PATH "${ARDUINO_CMAKE_SDK_PATH}/hardware/tools/avr/bin" CACHE PATH
+    set(ARDUINO_SDK_BIN_PATH "${ARDUINO_SDK_PATH}/hardware/tools/avr/bin" CACHE PATH
             "Path to Arduino SDK's binaries folder")
-    set(ARDUINO_SDK_ROOT_PATH "${ARDUINO_CMAKE_SDK_PATH}/hardware/tools/avr" CACHE PATH
+    set(ARDUINO_SDK_ROOT_PATH "${ARDUINO_SDK_PATH}/hardware/tools/avr" CACHE PATH
             "Path to Arduino SDK's sys-root folder")
-    set(ARDUINO_SDK_LIBRARIES_PATH "${ARDUINO_CMAKE_SDK_PATH}/libraries" CACHE PATH
+    set(ARDUINO_SDK_LIBRARIES_PATH "${ARDUINO_SDK_PATH}/libraries" CACHE PATH
             "Path to SDK's libraries directory")
-    set(ARDUINO_SDK_EXAMPLES_PATH "${ARDUINO_CMAKE_SDK_PATH}/examples" CACHE PATH
+    set(ARDUINO_SDK_EXAMPLES_PATH "${ARDUINO_SDK_PATH}/examples" CACHE PATH
             "Path to SDK's examples directory")
 
 endfunction()
@@ -52,14 +52,14 @@ endif ()
 set(ARDUINO_CMAKE_TOOLCHAIN_DIR ${CMAKE_CURRENT_LIST_DIR} CACHE PATH
         "Path to Arduino-CMake's toolchain directory")
 
+message("SDK: $ENV{ARDUINO_SDK_PATH}")
+
 # Set default path if none is set
-if (ARDUINO_SDK_PATH)
-    set(ARDUINO_CMAKE_SDK_PATH "${ARDUINO_SDK_PATH}" CACHE PATH "Arduino SDK Path")
+if ($ENV{ARDUINO_SDK_PATH})
+    set(ARDUINO_SDK_PATH "${ARDUINO_SDK_PATH}" CACHE PATH "Arduino SDK Path")
 else ()
-    if (NOT DEFINED ARDUINO_CMAKE_SDK_PATH) # Custom path has already been set
-        find_arduino_sdk(arduino_sdk_path)
-        set(ARDUINO_CMAKE_SDK_PATH "${arduino_sdk_path}" CACHE PATH "Arduino SDK Path")
-    endif ()
+    find_arduino_sdk(arduino_sdk_path)
+    set(ARDUINO_SDK_PATH "${arduino_sdk_path}" CACHE PATH "Arduino SDK Path")
 endif ()
 
 _setup_sdk_internal_paths()

cmake/Platform/Other/FindArduinoSDK.cmake

@@ -17,7 +17,7 @@ function(find_arduino_sdk _return_var)
 
     find_program(arduino_program_path
             NAMES arduino
-            PATHS ${platform_search_paths}
+            HINTS ${platform_search_paths}
             NO_DEFAULT_PATH
             NO_CMAKE_FIND_ROOT_PATH)
     get_filename_component(sdk_path "${arduino_program_path}" DIRECTORY)

cmake/Platform/System/PlatformInitializer.cmake

@@ -43,7 +43,7 @@ function(initialize_arduino_platform)
                 set(ARDUINO_CMAKE_PLATFORM_NAME "arduino" CACHE STRING "")
             endif ()
             set(ARDUINO_CMAKE_PLATFORM_ARCHITECTURE "avr" CACHE STRING "")
-            string(CONCAT platform_path "${ARDUINO_CMAKE_SDK_PATH}"
+            string(CONCAT platform_path "${ARDUINO_SDK_PATH}"
                     /hardware/
                     "${ARDUINO_CMAKE_PLATFORM_NAME}/"
                     "${ARDUINO_CMAKE_PLATFORM_ARCHITECTURE}")

cmake/Platform/System/VersionDetector.cmake

@@ -51,7 +51,7 @@ function(detect_sdk_version)
 
     find_file(ARDUINO_CMAKE_VERSION_FILE_PATH
             NAMES version.txt
-            PATHS "${ARDUINO_CMAKE_SDK_PATH}"
+            PATHS "${ARDUINO_SDK_PATH}"
             PATH_SUFFIXES lib
             DOC "Path to Arduino's version file"
             NO_CMAKE_FIND_ROOT_PATH)
@@ -86,6 +86,6 @@ function(detect_sdk_version)
     _get_normalized_sdk_version(normalized_sdk_version)
     set(runtime_ide_version "${normalized_sdk_version}" CACHE STRING "")
 
-    message(STATUS "Arduino SDK version ${ARDUINO_CMAKE_SDK_VERSION}: ${ARDUINO_CMAKE_SDK_PATH}")
+    message(STATUS "Arduino SDK version ${ARDUINO_CMAKE_SDK_VERSION}: ${ARDUINO_SDK_PATH}")
 
 endfunction()