add arm-features.h from glibc source (#12346)

lib/libc/glibc/sysdeps/arm/arm-features.h

@@ -0,0 +1,59 @@
+/* Macros to test for CPU features on ARM.  Generic ARM version.
+   Copyright (C) 2012-2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _ARM_ARM_FEATURES_H
+#define _ARM_ARM_FEATURES_H 1
+
+/* An OS-specific arm-features.h file should define ARM_HAVE_VFP to
+   an appropriate expression for testing at runtime whether the VFP
+   hardware is present.  We'll then redefine it to a constant if we
+   know at compile time that we can assume VFP.  */
+
+#ifndef __SOFTFP__
+/* The compiler is generating VFP instructions, so we're already
+   assuming the hardware exists.  */
+# undef ARM_HAVE_VFP
+# define ARM_HAVE_VFP	1
+#endif
+
+/* An OS-specific arm-features.h file may define ARM_ASSUME_NO_IWMMXT
+   to indicate at compile time that iWMMXt hardware is never present
+   at runtime (or that we never care about its state) and so need not
+   be checked for.  */
+
+/* A more-specific arm-features.h file may define ARM_ALWAYS_BX to indicate
+   that instructions using pc as a destination register must never be used,
+   so a "bx" (or "blx") instruction is always required.  */
+
+/* The log2 of the minimum alignment required for an address that
+   is the target of a computed branch (i.e. a "bx" instruction).
+   A more-specific arm-features.h file may define this to set a more
+   stringent requirement.
+
+   Using this only makes sense for code in ARM mode (where instructions
+   always have a fixed size of four bytes), or for Thumb-mode code that is
+   specifically aligning all the related branch targets to match (since
+   Thumb instructions might be either two or four bytes).  */
+#ifndef ARM_BX_ALIGN_LOG2
+# define ARM_BX_ALIGN_LOG2	2
+#endif
+
+/* An OS-specific arm-features.h file may define ARM_NO_INDEX_REGISTER to
+   indicate that the two-register addressing modes must never be used.  */
+
+#endif  /* arm-features.h */