abuild: always set CBUILD and CTARGET if unset

abuild.in

@@ -158,8 +158,6 @@ default_sanitycheck() {
 
 	# check if CARCH, CBUILD, CHOST and CTARGET is set
 	[ -z "$CHOST" ] && die "Please set CHOST in /etc/abuild.conf"
-	[ -z "$CBUILD" ] && CBUILD="$CHOST"
-	[ -z "$CTARGET" ] && CTARGET="$CHOST"
 
 	if [ -z "$CARCH" ]; then
 		die "Please fix CHOST, or set CARCH in abuild.conf"
@@ -1911,6 +1909,9 @@ if [ -z "$CLIBC" ]; then
 	esac
 fi
 
+[ -z "$CBUILD" ] && CBUILD="$CHOST"
+[ -z "$CTARGET" ] && CTARGET="$CHOST"
+
 cd "$startdir" || die
 . "$APKBUILD"