Improve avrdude and avrdude_conf path auto detection

In Arduino Linux distribution, avrdude and avrdude.conf files are placed
in different path. This commit improves the autodetection of avrdude
and avrdude.conf paths by considering this fact.

Fix #48

HISTORY.md

@@ -10,6 +10,7 @@ The following is the rough list of changes that went into different versions. I
 - Remove "utility" from example makefiles. Fix issue #84
 - Auto detect alternate core path from sketchbook folder. Fix issue #86
 - Remove redundant checks for ARDUINO_DIR
+- Improve avrdude and avrdude.conf path auto detection. Fix issue #48
 
 ### 0.12.0 (2013-06-20)
 - Fix "generated_assembly" target, which got broken earlier. Fix issue #76 (https://github.com/matthijskooijman)

arduino-mk/Arduino.mk

@@ -326,11 +326,27 @@ ifndef AVR_TOOLS_DIR
         AVR_TOOLS_DIR     = $(BUNDLED_AVR_TOOLS_DIR)
         $(call show_config_variable,AVR_TOOLS_DIR,[BUNDLED],(in Arduino distribution))
 
-        # if AVRDUDE_CONF is already defined, don't overwrite it
-        ifndef AVRDUDE_CONF
-            # The avrdude bundled with Arduino can't find it's config
-            AVRDUDE_CONF	  = $(AVR_TOOLS_DIR)/etc/avrdude.conf
-       endif
+        # In Linux distribution of Arduino, the path to avrdude and avrdude.conf are different
+        # More details at https://github.com/sudar/Arduino-Makefile/issues/48 and 
+        # https://groups.google.com/a/arduino.cc/d/msg/developers/D_m97jGr8Xs/uQTt28KO_8oJ
+        ifeq ($(CURRENT_OS),LINUX)
+
+            ifndef AVRDUDE
+                AVRDUDE = $(AVR_TOOLS_DIR)/../avrdude
+            endif
+
+            ifndef AVRDUDE_CONF
+                AVRDUDE_CONF = $(AVR_TOOLS_DIR)/../avrdude.conf
+            endif
+            
+        else
+
+            ifndef AVRDUDE_CONF
+                AVRDUDE_CONF  = $(AVR_TOOLS_DIR)/etc/avrdude.conf
+            endif
+
+        endif
+
     else
 
         SYSTEMPATH_AVR_TOOLS_DIR := $(call dir_if_exists,$(abspath $(dir $(shell which avr-gcc))/..))
@@ -345,6 +361,10 @@ else
     $(call show_config_variable,AVR_TOOLS_DIR,[USER])
 endif #ndef AVR_TOOLS_DIR
 
+ifndef AVR_TOOLS_PATH
+    AVR_TOOLS_PATH    = $(AVR_TOOLS_DIR)/bin
+endif
+
 ARDUINO_LIB_PATH  = $(ARDUINO_DIR)/libraries
 $(call show_config_variable,ARDUINO_LIB_PATH,[COMPUTED],(from ARDUINO_DIR))
 ARDUINO_CORE_PATH = $(ARDUINO_DIR)/hardware/arduino/cores/arduino
@@ -394,12 +414,6 @@ else
 
 endif
 
-ifdef AVR_TOOLS_DIR
-    ifndef AVR_TOOLS_PATH
-        AVR_TOOLS_PATH    = $(AVR_TOOLS_DIR)/bin
-    endif
-endif
-
 ########################################################################
 # Makefile distribution path
 #
@@ -881,19 +895,12 @@ $(OBJDIR)/%.sym: $(OBJDIR)/%.elf $(COMMON_DEPS)
 ########################################################################
 #
 # Avrdude
+# If avrdude is installed separately, it can find its own config file
 #
 ifndef AVRDUDE
     AVRDUDE          = $(AVR_TOOLS_PATH)/avrdude
 endif
 
-ifndef AVRDUDE_CONF
-    ifndef AVR_TOOLS_DIR
-        # The avrdude bundled with Arduino can't find its config
-        AVRDUDE_CONF  = $(AVR_TOOLS_DIR)/etc/avrdude.conf
-    endif
-    # If avrdude is installed separately, it can find its own config file
-endif
-
 # Default avrdude options. -V Do not verify, -q - suppress progress output
 ifndef AVRDUDE_OPTS
     AVRDUDE_OPTS = -q -V