AVR: ipa/92606 - Don't optimize PROGMEM data against non-PROGMEM.

AVR: ipa/92606 - Don't optimize PROGMEM data against non-PROGMEM.

ipa/92606: Inter-procedural analysis optimizes data across
address-spaces and PROGMEM.  As of v14, the PROGMEM part is
still not fixed (and there is still no target hook as proposed
in PR92932).  Just disable respective bogus optimization.

	PR ipa/92606
gcc/
	* config/avr/avr.cc (avr_option_override): Set
	flag_ipa_icf_variables = 0.
gcc/testsuite/
	* gcc.target/avr/torture/pr92606.c: New test.

(cherry picked from commit 08e752e72363ae7fd5a5fcb70913a0f7b240387b)