[sam] Added -MMD flag to tell compiler to produce dependencies files

Now a full rebuild of the sketch is triggered only if needed.

Author: cmaglie

build/shared/revisions.txt

@@ -4,6 +4,9 @@ ARDUINO 1.5.9
 [ide]
 * Updated AStyle formatter to v2.04: http://astyle.sourceforge.net/notes.html
 
+[core]
+* sam: added -MMD flag to let gcc produce dependency files (full rebuild on Arduino Due is now triggered only if needed)
+
 The following changes are included also in the Arduino IDE 1.0.7:
 
 [libraries]

hardware/arduino/sam/platform.txt

@@ -12,12 +12,12 @@ version=1.5.8
 
 compiler.path={runtime.ide.path}/hardware/tools/gcc-arm-none-eabi-4.8.3-2014q1/bin/
 compiler.c.cmd=arm-none-eabi-gcc
-compiler.c.flags=-c -g -Os -w -ffunction-sections -fdata-sections -nostdlib --param max-inline-insns-single=500 -Dprintf=iprintf
+compiler.c.flags=-c -g -Os -w -ffunction-sections -fdata-sections -nostdlib --param max-inline-insns-single=500 -Dprintf=iprintf -MMD
 compiler.c.elf.cmd=arm-none-eabi-gcc
 compiler.c.elf.flags=-Os -Wl,--gc-sections
 compiler.S.flags=-c -g -x assembler-with-cpp
 compiler.cpp.cmd=arm-none-eabi-g++
-compiler.cpp.flags=-c -g -Os -w -ffunction-sections -fdata-sections -nostdlib -fno-threadsafe-statics --param max-inline-insns-single=500 -fno-rtti -fno-exceptions -Dprintf=iprintf
+compiler.cpp.flags=-c -g -Os -w -ffunction-sections -fdata-sections -nostdlib -fno-threadsafe-statics --param max-inline-insns-single=500 -fno-rtti -fno-exceptions -Dprintf=iprintf -MMD
 compiler.ar.cmd=arm-none-eabi-ar
 compiler.ar.flags=rcs
 compiler.objcopy.cmd=arm-none-eabi-objcopy