Add SOC_FAMILY to the buildinfo file

Same machine target can be build for different SCO_FAMILY (H3/M3/M3N).
Add it to the buildinfo file, so we'll know which SOC_FAMILY was used.

Change-Id: I827a09c022ede0a7ec8e67bde431120f4de09e6a
Reviewed-by: Mikko Gronoff <mikko.gronoff@qt.io>

conf/distro/include/b2qt.inc

@@ -32,6 +32,8 @@ DEPLOY_CONF_NAME_m3ulcb     = "Renesas R-Car-M3 Starter Kit Pro"
 DEPLOY_CONF_NAME_h3ulcb     = "Renesas R-Car-H3 Starter Kit Premier"
 DEPLOY_CONF_NAME_salvator-x = "Renesas R-Car H3 M3 Salvator-X(S)"
 
+IMAGE_BUILDINFO_VARS:append = " SOC_FAMILY"
+
 IMAGE_FSTYPES += "wic.xz"
 DEPLOY_CONF_IMAGE_TYPE = "wic.xz"
 WKS_FILE = "sdimage-bootpart.wks"