Log messages about the platforms used in compilation

This should help debugging problems based on verbose compilation output,
especially if third-party boards and/or cores are involved. For example,
this might output:

	Using board 'pinoccio' from platform in folder: /path/to/sketchbook/hardware/pinoccio/avr
	Using core 'arduino' from platform in folder: /path/to/arduino/hardware/arduino/avr

Signed-off-by: Matthijs Kooijman <matthijs@stdin.nl>

Author: matthijskooijman

src/arduino.cc/builder/constants/constants.go

@@ -177,6 +177,8 @@ const MSG_UNHANDLED_TYPE_IN_CONTEXT = "Unhandled type {0} in context key {1}"
 const MSG_UNKNOWN_SKETCH_EXT = "Unknown sketch file extension: {0}"
 const MSG_USING_LIBRARY_AT_VERSION = "Using library {0} at version {1} in folder: {2} {3}"
 const MSG_USING_LIBRARY = "Using library {0} in folder: {1} {2}"
+const MSG_USING_BOARD = "Using board '{0}' from platform in folder: {1}"
+const MSG_USING_CORE = "Using core '{0}' from platform in folder: {1}"
 const MSG_USING_PREVIOUS_COMPILED_FILE = "Using previously compiled file: {0}"
 const MSG_WARNING_LIB_INVALID_CATEGORY = "WARNING: Category '{0}' in library {1} is not valid. Setting to '{2}'"
 const MSG_WARNING_PLATFORM_MISSING_VALUE = "Warning: platform.txt from core '{0}' misses property '{1}', using default value '{2}'. Consider upgrading this core."

src/arduino.cc/builder/target_board_resolver.go

@@ -100,6 +100,11 @@ func (s *TargetBoardResolver) Run(ctx *types.Context) error {
 		actualPlatform = targetPlatform
 	}
 
+	if ctx.Verbose {
+		logger.Println(constants.LOG_LEVEL_INFO, constants.MSG_USING_BOARD, targetBoard.BoardId, targetPlatform.Folder)
+		logger.Println(constants.LOG_LEVEL_INFO, constants.MSG_USING_CORE, core, actualPlatform.Folder)
+	}
+
 	ctx.BuildCore = core
 	ctx.ActualPlatform = actualPlatform