Add support for compilation on RaspberryPiZero (armv6)

More generally, add support for platforms with atomics, which not really linked to
architecture but compiler features. This may also help on some mips for example.

CHANGELOG.md

@@ -3,6 +3,7 @@ All notable changes to this project will be documented in this file.
 This project uses the changelog in accordance with [keepchangelog](http://keepachangelog.com/). Please use this to write notable changes, which is not the same as git commit log...
 
 ## [unreleased][unreleased]
+ - Add support for compilation on RaspberryPiZero (armv6) (@doegox)
  - Change: updates to README (@iceman)
  - Change: hf mf/mfu dbg => hw dbg (@doegox)
  - Change: replace usb_poll_validate_length() by data_available() that supports USART too (@doegox)

client/Makefile

@@ -31,7 +31,7 @@ platform = $(shell uname)
 VPATH = ../common ../zlib ../uart
 OBJDIR = obj
 
-LDLIBS = -L/opt/local/lib -L/usr/local/lib -lreadline -lpthread -lm
+LDLIBS = -L/opt/local/lib -L/usr/local/lib -lreadline -lpthread -lm -Wl,--as-needed -latomic -Wl,--no-as-needed
 LUALIB = ../liblua/liblua.a
 JANSSONLIBPATH = ./jansson
 JANSSONLIB = $(JANSSONLIBPATH)/libjansson.a

doc/md/Installation_Instructions/Linux-Installation-Instructions.md

@@ -13,7 +13,7 @@ You might want to follow one of these external resources to get an overview, but
 
 # Install the required dependencies
 
-## On Debian / Ubuntu / Kali / ParrotOS
+## On Debian / Ubuntu / Kali / ParrotOS / Raspbian
 
 First what we want to do is get an update for the system. If you need to upgrade do this **before** the install. An upgrade was carried out prior to following these instructions.