verification de la definition de ALLIANCE_TOP

et verifie aussi que ALLIANCE_TOP est bien un repertoire

alliance/src/alliance.m4

@@ -1,6 +1,16 @@
 AC_DEFUN(AM_ALLIANCE,
 [AC_REQUIRE([AM_INIT_AUTOMAKE])
 echo 'ALLIANCE configuration ....'
+if [ test "${ALLIANCE_TOP}" = "" ] ; then
+   echo '${ALLIANCE_TOP} not defined'
+   exit 1
+fi
+if [ test -d ${ALLIANCE_TOP} ] ; then
+   echo '${ALLIANCE_TOP} =' ${ALLIANCE_TOP}
+else
+   echo 'Bad directory for ${ALLIANCE_TOP} =' ${ALLIANCE_TOP}
+   exit 1
+fi
 INCLUDES=-I${ALLIANCE_TOP}/include
 LIBS=-L${ALLIANCE_TOP}/lib
 AC_SUBST(INCLUDES)