Compilation improvements by adding variant as other obj but not working on device

Arduino Zero devices with OpenOCD working

Created ARM_TOOLS_DIR and define arm toolchain executables in Sam.mk

Check avr-gcc on last AVR_TOOLS_DIR detect and indenting formatting

GDB debugging and programming added

Documentation updates and define ARDMK_VENDOR rather than include Sam.mk

Expand all parse_boards when defined rather than when used

Trim extra defines regex working on both macOS and Linux but need better fix

Print USB ids and added debug usage to readme

Add note on Arduino package dir and made board.txt work

Do ARM ARDUINO_ARCH define in Arduino.mk]

Add MZeroBlink to non-testable examples for now

Remove \B from extra defines grep

Add ARDUINO_PACKAGE_DIR for board support files

Fix a typo in the README

Fix typo in arduino-mk-vars.md

Prevent re-including Arduino.mk from Sam.mk when make restarts for upload

Add catrina to ARD_REST_OPTS if/else

Remove realpath in Sam.mk for cygwin compatability

SAMD bootloader support in ard-reset using --zero

Enters bootloader using open/close of port at 1200 BAUD, then polls the
attached devices for new port enumerating (bootloader). This is how the
Arduino IDE operates

Bossa support for Zero, MKR1000 etc

Re-word Arm README section after Native USB development

Reset for zero refactored like IDE

Zero bootloader reset tested on macOS and comments added

Re-word ARM bootloader and remove imports from testing

Patch changes ARDMK_VENDOR->ARCHITECHTURE, show_config_vars, ignore CORE_VER if emtpy

Common.mk header guard, openocd/bossac avoid separator, typos

Documentation update for patch changes

Move ARM tools to Sam.mk and auto-detect include

Correct accidental commit of Blink Makefile change

Lib fix with alternative core and documentation

Append zero to ARD_RESET_OPTS rather than set

Prioritise package ARM upload tools over path installed

Add note in README on ARM tools versions

Move openocd variant config script flag to OPTS