libc: Add Armv8.3-A PAuth and Armv8.5-A BTI compatibility to *.S

The most notable change is in sigsetjmp/siglongjmp. The former
stores LR signed with the current SP into jmp_buf. Calling siglongjmp
reads a signed LR and the corresponding SP from jmp_buf. This way not
only the checksum provides some means of integrity protection but
Pointer Authentication too.

Test: Tested on FVP with BTI enabled.

Change-Id: I9d720239775f8d2829a677901f546c4b14b5cbe5
diff --git a/libc/arch-arm64/generic/bionic/__memcpy_chk.S b/libc/arch-arm64/generic/bionic/__memcpy_chk.S
index a6eeca4..a8e9e83 100644
--- a/libc/arch-arm64/generic/bionic/__memcpy_chk.S
+++ b/libc/arch-arm64/generic/bionic/__memcpy_chk.S
@@ -43,3 +43,5 @@
 
   bl __memcpy_chk_fail
 END(__memcpy_chk)
+
+NOTE_GNU_PROPERTY()