🔨 Fix cmake build on Linux (#27605)

buildroot/share/cmake/CMakeLists.txt

@@ -1,15 +1,17 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 3.10)
 #====================================================================#
 # Usage under Linux:                                                 #
 #                                                                    #
-#    From Marlin/buildroot/share/cmake folder:                       #
+#    From the project folder:                                        #
+#        cd buildroot/share/cmake                                    #
 #        mkdir -p build && cd build                                  #
 #        cmake ..                                                    #
 #        make                                                        #
 #                                                                    #
 # Usage under Windows:                                               #
 #                                                                    #
-#    From Marlin/buildroot/share/cmake folder:                       #
+#    From the project folder:                                        #
+#        cd buildroot/share/cmake                                    #
 #        mkdir build && cd build                                     #
 #        cmake -G"Unix Makefiles" ..                                 #
 #        make                                                        #
@@ -82,10 +84,21 @@ message("-- Running CMake version: " ${CMAKE_VERSION})
 
 # Replace the CMake Ver. in the Arduino.cmake
 file(READ "${CMAKE_CURRENT_LIST_DIR}/marlin-cmake/Platform/Arduino.cmake" ORIGINAL_FILE_CONTENTS)
-string(REGEX REPLACE "cmake_minimum_required\\(VERSION[^\n]*\n" "cmake_minimum_required(VERSION 3.5)\n" NEW_FILE_CONTENTS "${ORIGINAL_FILE_CONTENTS}")
+string(REGEX REPLACE "cmake_minimum_required\\(VERSION[^\n]*\n" "cmake_minimum_required(VERSION 3.10)\n" NEW_FILE_CONTENTS "${ORIGINAL_FILE_CONTENTS}")
 file(WRITE "${CMAKE_CURRENT_LIST_DIR}/marlin-cmake/Platform/Arduino.cmake" "${NEW_FILE_CONTENTS}")
 
-set(CMAKE_MODULE_PATH  ${CMAKE_MODULE_PATH} ${CMAKE_CURRENT_LIST_DIR}/marlin-cmake/modules)
+# Fix "CMake Error... avr-gcc / avr-g++ is not a full path..."
+if(UNIX)
+  set(ORIGINAL_FILE_CONTENTS "")
+  set(NEW_FILE_CONTENTS "")
+  file(READ "${CMAKE_CURRENT_LIST_DIR}/marlin-cmake/toolchain/ArduinoToolchain.cmake" ORIGINAL_FILE_CONTENTS)
+  string(REPLACE "set(CMAKE_C_COMPILER   avr-gcc)\nset(CMAKE_CXX_COMPILER avr-g++)"
+                 "set(CMAKE_C_COMPILER   /usr/bin/gcc)\nset(CMAKE_CXX_COMPILER /usr/bin/gcc)"
+                 NEW_FILE_CONTENTS "${ORIGINAL_FILE_CONTENTS}")
+  file(WRITE "${CMAKE_CURRENT_LIST_DIR}/marlin-cmake/toolchain/ArduinoToolchain.cmake" "${NEW_FILE_CONTENTS}")
+endif(UNIX)
+
+set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${CMAKE_CURRENT_LIST_DIR}/marlin-cmake/modules)
 
 #====================================================================#
 #  Custom path to Arduino SDK can be set here                        #
@@ -116,6 +129,7 @@ set(CMAKE_TOOLCHAIN_FILE ${CMAKE_CURRENT_LIST_DIR}/marlin-cmake/toolchain/Arduin
 #   Go to the file in your CMake directory                           #
 #                                                                    #
 #   For Windows: cmake\Modules\Platform\WindowsPaths.cmake           #
+#   For macOS: cmake/Modules/Platform/UnixPaths.cmake                #
 #   For Linux: cmake/Modules/Platform/UnixPaths.cmake                #
 #                                                                    #
 #   Comment out "_cmake_record_install_prefix()"                     #