Fix build errors for armhf

Fix build errors for armhf

When building for 32-bit ARM, I ran into a couple build failures.

The first one seems to be caused by recent changes to warning switches,
leading to the following error:

--
In file included from gdb/coffread.c:35:0:
gdb/coffread.c: In function  "void enter_linenos(file_ptr, int, int, objfile*)":
gdb/complaints.h:40:40: error: format "%ld" expects argument of type "long int", but argument 2 has type "file_ptr {aka long long int}" [-Werror=format=]
  complaint_internal (FMT, ##__VA_ARGS__);  \
                                        ^
gdb/coffread.c:1413:7: note: in expansion of macro "complaint"
       complaint (_("Line number pointer %ld lower than start of line numbers"),
       ^~~~~~~~~
--

The other one is due to a narrowing conversion in valops.c:

--
gdb/valops.c: In function "value* value_assign(value*, value*)":
gdb/gdbtypes.h:1798:43: error: narrowing conversion of "type->type::length" from "ULONGEST {aka long long unsigned int}" to "size_t {aka unsigned int}" inside { } [-Werror=narrowing]
 #define TYPE_LENGTH(thistype) (thistype)->length
                               ~~~~~~~~~~~~^
gdb/valops.c:1252:9: note: in expansion of macro "TYPE_LENGTH"
         TYPE_LENGTH (type)});
--

Fix both with the following patch. Validated with --enable-targets=all on
Ubuntu 18.04/20.04.

gdb/ChangeLog:

2021-01-21  Luis Machado  <luis.machado@linaro.org>

	* coffread.c (enter_linenos): Passing string to complaint.
	* valops.c (value_assign): Make array view.