config.mk: Add MK_VIMAGE knob

Default to VIMAGE as yes.
Add VIMAGE to __DEFAULT_DEPENDENT_OPTIONS (to define VIMAGE_SUPPORT)

Only output VIMAGE to opt_global.h when VIMAGE support is wanted.

Obtained from:	Juniper Networks, Inc.
Differential Revision:	https://reviews.freebsd.org/D39636

share/mk/src.opts.mk

@@ -184,6 +184,7 @@ __DEFAULT_YES_OPTIONS = \
     USB \
     UTMPX \
     VI \
+    VIMAGE \
     VT \
     WIRELESS \
     WPA_SUPPLICANT_EAPOL \
@@ -249,6 +250,7 @@ __LIBC_MALLOC_DEFAULT=	jemalloc
     NETGRAPH \
     PAM \
     TESTS \
+    VIMAGE \
     WIRELESS
 __DEFAULT_DEPENDENT_OPTIONS+= ${var}_SUPPORT/${var}
 .endfor

sys/conf/config.mk

@@ -11,7 +11,9 @@ opt_global.h:
 	touch ${.TARGET}
 	@echo "#define SMP 1" >> ${.TARGET}
 	@echo "#define MAC 1" >> ${.TARGET}
+.if ${MK_VIMAGE_SUPPORT} != "no"
 	@echo "#define VIMAGE 1" >> ${.TARGET}
+.endif
 # Note: Define 'options' in DEFAULTS to 1. For simplicity, no check if the
 # option is in opt_global.h. Nearly all the options in DEFAUlTS today are in
 # opt_global.h with GEOM_* being the main exceptions. Move any options from

sys/conf/kern.opts.mk

@@ -52,6 +52,7 @@ __DEFAULT_YES_OPTIONS = \
     SPLIT_KERNEL_DEBUG \
     TESTS \
     USB_GADGET_EXAMPLES \
+    VIMAGE \
     ZFS
 
 __DEFAULT_NO_OPTIONS = \
@@ -182,7 +183,8 @@ OPT_${opt}:=	${rep}
 #
 .for var in \
     INET \
-    INET6
+    INET6 \
+    VIMAGE
 .if defined(WITHOUT_${var}_SUPPORT) || ${MK_${var}} == "no"
 MK_${var}_SUPPORT:= no
 .else