[PATCH] avoid copying inlining attributes in attribute copy

[Martin Sebor]

Enabling in Glibc the recent enhancement to detect attribute
mismatches in alias declarations (PR 81824) revealed a use
case where aliases are being declared for targets declared
with the always_inline attribute.  Copying the always_inline
attribute to the declaration of the alias would then trigger

   error: always_inline function might not be inlinable [-Werror=attributes]

due to the alias not being inlinable in some contexts where
(presumably) the target would be.  To avoid the warning for
this use case the attached patch excludes all attributes
that affect inlining from being copied by attribute copy.

While testing this I also more thoroughly exercised attribute
tls_target (which also came up during the Glibc deployment),
and improved the diagnostics for the attribute to make their
root cause easier to understand (printing "attribute ignored"
alone isn't very informative without also explaining why).

Martin

PS While testing this I also opened bug 88010 where inlining
attributes on aliases seem to be silently ignored in favor of
those on their targets.  I'm wondering what the expected (or
preferred) behavior is.
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