Exporting ENV vars from Makefile is supported only with GNU Make. Use the shell instead.

plugins-scripts/Makefile.am

@@ -6,8 +6,6 @@ NP-VERSION-FILE: .FORCE-NP-VERSION-FILE
 
 -include NP-VERSION-FILE
 
-export NP_VERSION:= $(NP_VERSION)
-
 SUFFIXES = .pl .sh
 
 VPATH=$(top_srcdir) $(top_srcdir)/plugins-scripts $(top_srcdir)/plugins-scripts/t
@@ -39,11 +37,11 @@ test-debug:
 CLEANFILES=$(libexec_SCRIPTS)
 
 .pl :
-	$(AWK) -f ./subst $< > $@
+	NP_VERSION=$(NP_VERSION) $(AWK) -f ./subst $< > $@
 	chmod +x $@
 
 .sh :
-	$(AWK) -f ./subst $< > $@
+	NP_VERSION=$(NP_VERSION) $(AWK) -f ./subst $< > $@
 	chmod +x $@
 
 clean-local: