ipa/92606 - properly handle no_icf attribute for variables
The following adds no_icf handling for variables where the attribute
was rejected. It also fixes the check for no_icf by checking both
the source and the targets decl.
PR ipa/92606
gcc/c-family/
* c-attribs.cc (handle_noicf_attribute): Also allow the
attribute on global variables.
gcc/
* ipa-icf.cc (sem_item_optimizer::merge_classes): Check
both source and alias for the no_icf attribute.
* doc/extend.texi (no_icf): Document variable attribute.