fw update: spi device code updater

This code updater is for updating spi flash devices.
It can for example update the host firmware on different server boards
and has following features:

- power down the host before update
- set mux gpios to access spi flash
- (very limited) communication with ME (Management Engine)
- use flashrom to utilize fw with IFD (Intel Flash Descriptor)
- otherwise directly write to the flash chip.

The behavior of this code updater can be configured via EM.

Tested: on Tyan S5549 Board

Change-Id: I27803b7fded71af2364c2f55fad841a410603dec
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/meson.build b/meson.build
index 8db7902..370b489 100644
--- a/meson.build
+++ b/meson.build
@@ -66,7 +66,7 @@
 
 common_include = include_directories('.')
 
-common_build = build_tests.allowed()
+common_build = build_tests.allowed() or get_option('code-updater-spi-device').enabled()
 
 if common_build
   libpldm_dep = dependency('libpldm')
@@ -80,7 +80,10 @@
   subdir('common')
 endif
 
+if get_option('code-updater-spi-device').enabled()
+  subdir('bios-spi')
+endif
+
 if build_tests.allowed()
   subdir('test')
 endif
-