rs6000: Fix up flag_shrink_wrap handling in presence of -mrop-protect [PR101324]

PR101324 shows a problem in disabling shrink-wrapping when using -mrop-protect
when there is a attribute optimize/pragma.  The fix envolves moving the handling
of flag_shrink_wrap so it gets re-disbled when we change or add options.

2021-12-03  Martin Liska  <mliska@suse.cz>

gcc/
	PR target/101324
	* config/rs6000/rs6000.c (rs6000_option_override_internal): Move the
	disabling of shrink-wrapping when using -mrop-protect from here...
	(rs6000_override_options_after_change): ...to here.

2021-12-03  Peter Bergner  <bergner@linux.ibm.com>

gcc/testsuite/
	PR target/101324
	* gcc.target/powerpc/pr101324.c: New test.