libm: Add Armv8.3-A PAuth and Armv8.5-A BTI support to assembly files

This change adds both Armv8.3-A Pointer Authentication and Armv8.5-A BTI
support to *.S files.

Tests: Tested on FVP with BTI enabled

Change-Id: I82750afcbc950a91584463fbc979c2c35d41916a
diff --git a/libm/arm64/sqrt.S b/libm/arm64/sqrt.S
index 3a58ef3..0659b13 100644
--- a/libm/arm64/sqrt.S
+++ b/libm/arm64/sqrt.S
@@ -25,3 +25,5 @@
   fsqrt s0, s0
   ret
 END(sqrtf)
+
+NOTE_GNU_PROPERTY()