zdtm: handle COMPAT_TEST from Makefile.inc

In this case it will work for any make commangs. For example:
make COMPAT_TEST=y -C test/zdtm/lib

travis-ci: success for zdtm: handle COMPAT_TEST from Makefile.inc
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm/Makefile

 SUBDIRS	=	lib static transition
 
-ifeq ($(COMPAT_TEST),y)
-ifeq ($(ARCH),x86)
-        export USERCFLAGS += -m32
-        export CFLAGS += -m32
-        export LDFLAGS += -m32
-endif
-endif
-
 default:	all
 .PHONY: default lib static transition
 

test/zdtm/Makefile.inc

@@ -30,4 +30,12 @@ endif
 
 RM := rm -f --one-file-system
 
+ifeq ($(COMPAT_TEST),y)
+ifeq ($(ARCH),x86)
+        export USERCFLAGS += -m32
+        export CFLAGS += -m32
+        export LDFLAGS += -m32
+endif
+endif
+
 export E Q RM