testsuite: Add missing require target fpic

Add requirement for effective target fpic for tests explicitly passing
the "-fpic" and "-fPIC" options.

This fixes spurious failures on pru-unknown-elf, avr and probably
others.

gcc/testsuite/ChangeLog:

	* g++.dg/gcov/gcov-12.C: Require effective target fpic.
	* g++.old-deja/g++.mike/eh30.C: Ditto.
	* g++.old-deja/g++.mike/p4750.C: Ditto.
	* g++.old-deja/g++.robertl/eb106.C: Ditto.

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>