Use function attributes for SSE 4.2 even when targeting that extension

On Red Hat 9 systems (or similar), the packaged gcc targets x86-64-v2,
but clang does not. This has caused build failures in the wake of
commit e2809e3 when building --with-llvm.

The most expedient fix is to use the same function attributes for
the inlined function as we do for the global function.

Reported-by: Kyotaro Horiguchi <[email protected]> (plus members skimmer and bumblebee)
Diagnosed-by: Tom Lane <[email protected]>
Tested-by: Todd Cook <[email protected]>
Discussion: https://postgr.es/m/CANWCAZZSxs3a1YRKehkgk2OHKbrVn+xZ+AWW8Co2R_f70NqqmA@mail.gmail.com

Author: j-naylor

src/include/port/pg_crc32c.h

@@ -52,7 +52,13 @@ typedef uint32 pg_crc32c;
 
 extern pg_crc32c pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len);
 
+/*
+ * We can only get here if the host compiler targets SSE 4.2, but on some
+ * systems gcc and clang don't have the same built-in targets, so we still
+ * must use a function attribute here to accommodate "--with-llvm" builds.
+ */
 pg_attribute_no_sanitize_alignment()
+pg_attribute_target("sse4.2")
 static inline
 pg_crc32c
 pg_comp_crc32c_dispatch(pg_crc32c crc, const void *data, size_t len)