meson: Build the ich_descriptors_tool as feature

Provide the meson option `-Dich_descriptors_tool=auto/enable/disabled`
to determin if the ich_descriptors_tool should be build or not. On
`auto` or `enabled` it will be, on `disabled` it will not be build.
This is usefull for environments where the ich_descriptors_tool is not
needed.

Change-Id: Ief65a914019f72536d563eda36bd7f2f5330bea8
Signed-off-by: Thomas Heijligen <thomas.heijligen@secunet.com>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/66704
Original-Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72345
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/meson.build b/meson.build
index 03ffbc9..2374b00 100644
--- a/meson.build
+++ b/meson.build
@@ -469,4 +469,6 @@
   link_with : libflashrom.get_static_lib(), # flashrom needs internal symbols of libflashrom
 )
 
-subdir('util')
+if get_option('ich_descriptors_tool').auto() or get_option('ich_descriptors_tool').enabled()
+  subdir('util/ich_descriptors_tool')
+endif