firmware: replace libnewlib with picolibc

libnewlib-arm-none-eabi has been removed in debian unstable, build the
firmware with picolibc instead.

Fixes: OS#7017
Change-Id: If136397b71435ea0850002ef6406067962e8d4d7

debian/control

@@ -12,7 +12,7 @@ Build-Depends: debhelper (>= 10),
                dh-autoreconf,
                libosmocore-dev (>= 1.11.0),
                libpcsclite-dev,
-               libnewlib-arm-none-eabi,
+               picolibc-arm-none-eabi,
                libusb-1.0-0-dev,
                gcc-arm-none-eabi
 Standards-Version: 3.9.8

firmware/Makefile

@@ -171,6 +171,7 @@ INCLUDES += -Ilibcommon/include
 INCLUDES += -Ilibosmocore/include
 INCLUDES += -Isrc_simtrace -Iinclude
 INCLUDES += -Iapps/$(APP)
+INCLUDES += -I/usr/lib/picolibc/arm-none-eabi/include
 
 ifneq ("$(USE_CLANG)","0")
 CFLAGS += -Wno-unknown-warning-option -Wno-empty-body -fno-exceptions -fno-unwind-tables --config armv7em_soft_nofp_nosys