libm: Add .section .note.GNU-stack to all assembly files

libm: Add .section .note.GNU-stack to all assembly files

GCC always appends the following line to assembly files it generates:

  .section    .note.GNU-stack,"",@progbits

This creates an empty section named ".note.GNU-stack" to the object file
which servers as a hint to GNU linkers that this object file does not
require an executable stack.  When all linked object files indicate that
no executable stack is needed, the executable NX bit is set such as the
binary is run on a non-executable stack.  This is a free security
improvement against buffer overflow attacks.