lto-wrapper: fix memory corruption.

lto-wrapper: fix memory corruption.

The first argument of merge_and_complain is actually vector where
we merge options and it should be propagated to caller properly.

Fixes:

==6656== Invalid read of size 8
==6656==    at 0x408056: merge_and_complain (lto-wrapper.c:335)
==6656==    by 0x408056: find_and_merge_options(int, long, char const*, vec<cl_decoded_option, va_heap, vl_ptr>, vec<cl_decoded_option, va_heap, vl_ptr>*, char const*) (lto-wrapper.c:1139)
==6656==    by 0x408AFC: run_gcc(unsigned int, char**) (lto-wrapper.c:1505)
==6656==    by 0x4061A2: main (lto-wrapper.c:2138)
==6656==  Address 0x4e69b18 is 344 bytes inside a block of size 1,768 free'd
==6656==    at 0x484339F: realloc (vg_replace_malloc.c:1192)
==6656==    by 0x4993C0: xrealloc (xmalloc.c:181)
==6656==    by 0x406A82: reserve<cl_decoded_option> (vec.h:290)
==6656==    by 0x406A82: reserve (vec.h:1858)
==6656==    by 0x406A82: vec<cl_decoded_option, va_heap, vl_ptr>::safe_push(cl_decoded_option const&) [clone .isra.0] (vec.h:1967)
==6656==    by 0x4077E0: merge_and_complain (lto-wrapper.c:457)
==6656==    by 0x4077E0: find_and_merge_options(int, long, char const*, vec<cl_decoded_option, va_heap, vl_ptr>, vec<cl_decoded_option, va_heap, vl_ptr>*, char const*) (lto-wrapper.c:1139)
==6656==    by 0x408AFC: run_gcc(unsigned int, char**) (lto-wrapper.c:1505)
==6656==    by 0x4061A2: main (lto-wrapper.c:2138)
==6656==  Block was alloc'd at
==6656==    at 0x483E70F: malloc (vg_replace_malloc.c:380)
==6656==    by 0x4993D7: xrealloc (xmalloc.c:179)
==6656==    by 0x407476: reserve<cl_decoded_option> (vec.h:290)
==6656==    by 0x407476: reserve (vec.h:1858)
==6656==    by 0x407476: reserve_exact (vec.h:1878)
==6656==    by 0x407476: create (vec.h:1893)
==6656==    by 0x407476: get_options_from_collect_gcc_options(char const*, char const*) (lto-wrapper.c:163)
==6656==    by 0x407674: find_and_merge_options(int, long, char const*, vec<cl_decoded_option, va_heap, vl_ptr>, vec<cl_decoded_option, va_heap, vl_ptr>*, char const*) (lto-wrapper.c:1132)
==6656==    by 0x408AFC: run_gcc(unsigned int, char**) (lto-wrapper.c:1505)
==6656==    by 0x4061A2: main (lto-wrapper.c:2138)

gcc/ChangeLog:

	* lto-wrapper.c (merge_and_complain): Make the first argument
	a reference type.