linux: added linux target

* add toolchain file
* add linux to preview targets
* add stub for dfu number in cmake
* excluded unity runner per default
* Added esp_attr.h and esp_partition.h linux stubs
* component.cmake check list for emptyness
* added switch for linux in unity cmake file
* Added Linux host example app

components/unity/CMakeLists.txt

@@ -1,6 +1,9 @@
 set(srcs
-    "unity/src/unity.c"
-    "unity_port_esp32.c")
+    "unity/src/unity.c")
+
+set(includes
+    "include"
+    "unity/src")
 
 if(CONFIG_UNITY_ENABLE_BACKTRACE_ON_FAIL)
     list(APPEND COMPONENT_PRIV_INCLUDEDIRS "include/priv")
@@ -12,13 +15,24 @@ endif()
 
 if(CONFIG_UNITY_ENABLE_FIXTURE)
     list(APPEND srcs "unity/extras/fixture/src/unity_fixture.c")
+    list(APPEND includes "unity/extras/fixture/src")
+endif()
+
+if(${IDF_TARGET} STREQUAL "linux")
+    message(STATUS "adding linux stuff...")
+    idf_component_get_property(spi_flash_dir spi_flash COMPONENT_DIR)
+    list(APPEND includes "${spi_flash_dir}/sim/stubs/esp_common")
+else()
+    list(APPEND srcs "unity_port_esp32.c")
 endif()
 
 idf_component_register(SRCS "${srcs}"
                     INCLUDE_DIRS "include" "unity/src" "unity/extras/fixture/src")
 
-target_compile_definitions(${COMPONENT_LIB} PUBLIC
-    -DUNITY_INCLUDE_CONFIG_H
-)
+if(NOT ${IDF_TARGET} STREQUAL "linux")
+    target_compile_definitions(${COMPONENT_LIB} PUBLIC
+        -DUNITY_INCLUDE_CONFIG_H
+    )
+endif()
 
 target_compile_options(${COMPONENT_LIB} PRIVATE -Wno-unused-const-variable)