[patch][avr] New option -nodevicespecs to omit -specs=... in self specs.

[Jeff Law]

On Wed, 2019-12-18 at 16:36 +0100, Georg-Johann Lay wrote:
> Hi, currently device support in avr-gcc is accomplished by injecting a 
> specs file my means of -specs=... in dirver self specs.
> 
> This patch adds a new avr driver option to omit the addition of 
> respective -specs option so give the user more freedom.
> 
> Ok to apply?
> 
> Johann
> 
> 	* config/avr/avr.opt (-nodevicespecs): New driver option.
> 	* config/avr/driver-avr.c (avr_devicespecs_file): Only issue
> 	"-specs=device-specs/..." if that option is not set.
> 	* doc/invoke.texi (AVR Options) <-nodevicespecs>: Document.
OK
jeff