Fix GDB build failure when $development is false

Fix GDB build failure when $development is false

We don't build GDB selftests bits when $development is false.  However, if
we turn bfd/development.sh:$development to false, common/selftest.c is
compiled which is not expected.  It causes the build failure,

selftest.o: In function `selftests::run_tests(char const*)':
binutils-gdb/gdb/common/selftest.c:97: undefined reference to `selftests::reset()'
collect2: error: ld returned 1 exit status

I fix this issue by putting selftest.o selftest-arch.o into CONFIG_OBS
only when $development is true.  After this is fixed, there are other
build failures in maint.c, this patch fixes them as well.

In the release mode, the output of these commands are:

(gdb) maintenance selftest
Selftests are not available in a non-development build.
(gdb) maintenance selftest foo
Selftests are not available in a non-development build.
(gdb) maintenance info selftests
Selftests are not available in a non-development build.

gdb:

2018-01-08  Yao Qi  <yao.qi@linaro.org>
	    Simon Marchi  <simon.marchi@ericsson.com>

	* Makefile.in (COMMON_SFILES): Remove selftest-arch.c and
	common/selftest.c.
	(COMMON_OBS): Remove selftest.o.
	* configure.ac: Append selftest-arch.c and common/selftest.c to
	CONFIG_SRCS.  Append selftest-arch.o and selftest.o to COMMON_OBS.
	* configure: Re-generated.
	* maint.c (maintenance_selftest): Wrap selftests::run_tests with
	GDB_SELF_TEST.
	(maintenance_info_selftests): Likewise.

gdb/testsuite:

2018-01-08  Simon Marchi  <simon.marchi@ericsson.com>

	* gdb.gdb/unittest.exp: Match output in non-development mode.