[PATCH][AArch64] Add unwind info to __libc_start_main

[Wilco Dijkstra]

Add unwind info to __libc_start_main so that unwinding continues one
extra level to _start.

ChangeLog:
2017-07-31  Wilco Dijkstra  <wdijkstr@arm.com>

        * sysdeps/aarch64/Makefile: Build libc-start.c with -fexceptions.

--
diff --git a/sysdeps/aarch64/Makefile b/sysdeps/aarch64/Makefile
index 562c1373aebee6ffb4ff5c2071a23d007a8e07ba..81bb01923d18856b609632251a83d93a6e995b46 100644
--- a/sysdeps/aarch64/Makefile
+++ b/sysdeps/aarch64/Makefile
@@ -11,6 +11,8 @@ endif
 
 ifeq ($(subdir),csu)
 gen-as-const-headers += tlsdesc.sym
+
+CFLAGS-libc-start.c += -fexceptions
 endif
 
 ifeq ($(subdir),gmon)