Let the assembler handle the low-level details of generating .eh_frame,
and use .cfi_escape to output the DWARF3 DW_CFA_def_cfa_expression and
DW_CFA_expression instructions.
Explicitly output a nop instruction between the FDE start
(.cfi_startproc) and the trampoline symbol.
x86_64: remove the rsp instruction, which is redundant with the CFA
itself.
Bug: http://b/169383888
Test: compare `objdump -Wf` output before and after
Test: bionic-unit-tests
Change-Id: Ie2a6d111cb473596be8c9f4fd64534e91d88f2a1
fd8d687051