Fixes compilation in external mode

src/plugins/e-acsl/Makefile.in

@@ -41,6 +41,14 @@ else
 EACSL_HAS_OCAML312 = yes
 endif
 
+# Utilities used to create the list of contrib/ files to be included in the
+# distribution. In external mode, we can't rely on these variables to be
+# set, as we have to build the list before including Makefile.dynamic.
+# There is no real alternative to cat and sed anyways, which are both part of
+# POSIX, so that the usefulness of the variables is questionable.
+CAT?=cat
+SED?=sed
+
 #########################
 # Plug-in configuration #
 #########################
@@ -258,7 +266,7 @@ PLUGIN_DISTRIB_EXTERNAL:=\
   $(EACSL_LICENSE_FILES) \
   $(EACSL_CONTRIB_FILES)
 
-EACSL_DISTRIB_FILES:= $(PLUGIN_DISTRIB_FILES) $(EACSL_OCAML_FILES)
+EACSL_DISTRIB_FILES:= $(PLUGIN_DISTRIB_EXTERNAL) $(EACSL_OCAML_FILES)
 
 # BE CAREFUL: manually remove all *.ml* files which should not be released!
 e-acsl-distrib: .depend