x86: Add x86_64 to x86-64 HWCAP [BZ #22093]

Before glibc 2.26, ld.so set dl_platform to "x86_64" and searched the
"x86_64" subdirectory when loading a shared library.  ld.so in glibc
2.26 was changed to set dl_platform to "haswell" or "xeon_phi", based
on supported ISAs.  This led to shared library loading failure for
shared libraries placed under the "x86_64" subdirectory.

This patch adds "x86_64" to x86-64 dl_hwcap so that ld.so will always
search the "x86_64" subdirectory when loading a shared library.

NB: We can't set x86-64 dl_platform to "x86-64" since ld.so will skip
the "haswell" and "xeon_phi" subdirectories on "haswell" and "xeon_phi"
machines.

Tested on i686 and x86-64.

	[BZ #22093]
	* sysdeps/x86/cpu-features.c (init_cpu_features): Initialize
	GLRO(dl_hwcap) to HWCAP_X86_64 for x86-64.
	* sysdeps/x86/dl-hwcap.h (HWCAP_COUNT): Updated.
	(HWCAP_IMPORTANT): Likewise.
	(HWCAP_X86_64): New enum.
	(HWCAP_X86_AVX512_1): Updated.
	* sysdeps/x86/dl-procinfo.c (_dl_x86_hwcap_flags): Add "x86_64".
	* sysdeps/x86_64/Makefile (tests): Add tst-x86_64-1.
	(modules-names): Add x86_64/tst-x86_64mod-1.
	(LDFLAGS-tst-x86_64mod-1.so): New.
	($(objpfx)tst-x86_64-1): Likewise.
	($(objpfx)x86_64/tst-x86_64mod-1.os): Likewise.
	(tst-x86_64-1-clean): Likewise.
	* sysdeps/x86_64/tst-x86_64-1.c: New file.
	* sysdeps/x86_64/tst-x86_64mod-1.c: Likewise.

1 files changed, 2 insertions, 2 deletions

diff --git a/sysdeps/x86/dl-procinfo.c b/sysdeps/x86/dl-procinfo.c
index 43ab8fe25b..0192feb850 100644
--- a/sysdeps/x86/dl-procinfo.c
+++ b/sysdeps/x86/dl-procinfo.c
@@ -58,11 +58,11 @@ PROCINFO_CLASS struct cpu_features _dl_x86_cpu_features
 #if !defined PROCINFO_DECL && defined SHARED
   ._dl_x86_hwcap_flags
 #else
-PROCINFO_CLASS const char _dl_x86_hwcap_flags[2][9]
+PROCINFO_CLASS const char _dl_x86_hwcap_flags[3][9]
 #endif
 #ifndef PROCINFO_DECL
 = {
-    "sse2", "avx512_1"
+    "sse2", "x86_64", "avx512_1"
   }
 #endif
 #if !defined SHARED || defined PROCINFO_DECL