Add giga packaging script

Author: facchinm

giga.variables

@@ -0,0 +1,5 @@
+export FLAVOUR="giga"
+export VARIANTS=("GIGA")
+export FQBNS=("giga")
+export LIBRARIES=("doom Ethernet MRI Portenta_SDRAM SPI WiFi ea_malloc openamp_arduino STM32H747_System ThreadDebug Himax_HM01B0 PDM Portenta_Video USBAudio KernelDebug Portenta_Audio RPC USBHID Wire Portenta_lvgl Camera rpclib USBHOST mbed-memory-status Portenta_SDCARD Scheduler USBMSD SocketWrapper GSM GPS MCUboot")
+export BOOTLOADERS=("GIGA")