NVS flash: host-based unit test of nvs::Page

* General tests like page loading from flash
* Rough test of fixed-size data types
* Rough test of blob read
* Added coverage target in cmake, also accessible
  via `idf.py coverage`
* Fixed unsigned comparison in comp. enum table
* introducing temporary LINUX_TARGET define

components/nvs_flash/CMakeLists.txt

@@ -1,3 +1,5 @@
+idf_build_get_property(target IDF_TARGET)
+
 set(srcs "src/nvs_api.cpp"
          "src/nvs_cxx_api.cpp"
          "src/nvs_item_hash_list.cpp"
@@ -11,10 +13,39 @@ set(srcs "src/nvs_api.cpp"
          "src/nvs_partition_manager.cpp"
          "src/nvs_types.cpp")
 
-if(CONFIG_NVS_ENCRYPTION)
-    list(APPEND srcs "src/nvs_encrypted_partition.cpp")
-endif()
+set(public_req spi_flash)
+
+set(include_dirs "include")
 
 idf_component_register(SRCS "${srcs}"
-                    REQUIRES spi_flash mbedtls
-                    INCLUDE_DIRS include)
+                    REQUIRES "${public_req}"
+                    INCLUDE_DIRS "${include_dirs}")
+
+# If we use the linux target, we need to redirect the crc functions to the linux
+if(${target} STREQUAL "linux")
+    if(CONFIG_NVS_ENCRYPTION)
+        # mbedtls isn't configured for building with linux or as mock target. It will draw in all kind of dependencies
+        message(FATAL_ERROR "NVS currently doesn't support encryption if built for Linux.")
+    endif()
+    idf_component_get_property(spi_flash_dir spi_flash COMPONENT_DIR)
+    target_include_directories(${COMPONENT_LIB} PUBLIC
+            "${CMAKE_CURRENT_SOURCE_DIR}/mock/int"
+            "${spi_flash_dir}/sim/stubs/freertos/include")
+    target_sources(${COMPONENT_LIB} PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}/mock/int/crc.cpp")
+    target_compile_options(${COMPONENT_LIB} PUBLIC "-DLINUX_TARGET")
+else()
+    # TODO: this is a workaround until IDF-2085 is fixed
+    idf_component_get_property(mbedtls_lib mbedtls COMPONENT_LIB)
+    target_link_libraries(${COMPONENT_LIB} PUBLIC ${mbedtls_lib})
+endif()
+
+if(CONFIG_NVS_ENCRYPTION)
+    target_sources(${COMPONENT_LIB} PRIVATE "src/nvs_encrypted_partition.cpp")
+    idf_component_get_property(mbedtls_lib mbedtls COMPONENT_LIB)
+    target_link_libraries(${COMPONENT_LIB} PUBLIC ${mbedtls_lib})
+endif()
+
+if(${target} STREQUAL "linux")
+    target_compile_options(${COMPONENT_LIB} PUBLIC --coverage)
+    target_link_libraries(${COMPONENT_LIB} PUBLIC --coverage)
+endif()