Make: create PHONY for standalone

This is good practice for targets that do not create
particular files.
Merge pull request #1337 from peabody124/phony_standalone

Make: create PHONY for standalone
ChibiOS: Pristine import of v2.6.6
ChibiOS: fix GPIOv2 conflict with st libs GPIO_TypeDef
ChibiOS: remove CMSIS arm_math.h to prevent conflict
ChibiOS: disable stm32f30x usb irq relocation for legacy compatibility
pios_semaphore: fix mismatched comment
pios_semaphore: add ChibiOS implementation
pios_semaphore: fix simulation exception
pios_mutex: add ChibiOS implementation
pios_thread: add ChibiOS implementation
pios_queue: add ChibiOS implementation
pios_com: add support for ChibiOS
pios/common: add support for ChibiOS
GenericI2CSensor/i2c_vm: add support for ChibiOS
System: add support for ChibiOS
pios/stm32f4xx: add pios_chibios_transition_priv.h
pios/stm32f4xx: add support for ChibiOS
pios stm32f4xx: added ChibiOS IRQ prologue and epilogue macros
pios/stm32f30x: add support for ChibiOS