meson: fix various meson build warnings and formatting

- Make run_command() calls check for failures to fix warnings about
  ignoring errors, see https://github.com/mesonbuild/meson/issues/9300.

- Remove `include_directories('../subprojects')` from tests/meson.build.
  It isn't necessary and caused build warnings due to referencing files
  outside the tests/ directory.

- Fix indent level and formatting in a few places.

BUG=none
BRANCH=none
TEST=meson; ninja; ninja test

Change-Id: I17ae0c51d68ed004772a237641f08345f4893200
Signed-off-by: Nikolai Artemiev <nartemiev@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/66060
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Thomas Heijligen <src@posteo.de>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>

tests/meson.build

@@ -11,8 +11,6 @@
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 
-root_includes = include_directories('../subprojects')
-
 srcs = [
   'io_mock.c',
   'tests.c',
@@ -105,7 +103,6 @@ mocks = [
 
 flashrom_tests = executable('flashrom_unit_tests',
   srcs,
-  include_directories : root_includes,
   c_args : [
     cargs,
     '-ffunction-sections',