Fix (merge?) error in generated_headers.am

Instead of listing all prerequisites multiple rules were added for the
same target, probably while doing a merge

generated_headers.am

@@ -13,13 +13,9 @@ config-f90.h: config.h
 	@echo "Generating $@...";
 	@grep "^#define" $^ > $@ || { rm $@; exit 1; }
 
-elpa/elpa_generated.h: $(top_srcdir)/src/elpa_driver/legacy_interface/elpa_driver_c_interface_legacy.F90 | elpa
-	$(call extract_interface,!c>)
-
-elpa/elpa_generated.h: $(top_srcdir)/src/elpa1/legacy_interface/elpa_1stage_c_interface_legacy.F90 | elpa
-	$(call extract_interface,!c>)
-
-elpa/elpa_generated.h: $(top_srcdir)/src/elpa2/legacy_interface/elpa_2stage_c_interface_legacy.F90 | elpa
+elpa/elpa_generated.h: $(top_srcdir)/src/elpa_driver/legacy_interface/elpa_driver_c_interface_legacy.F90 \
+                       $(top_srcdir)/src/elpa1/legacy_interface/elpa_1stage_c_interface_legacy.F90 \
+                       $(top_srcdir)/src/elpa2/legacy_interface/elpa_2stage_c_interface_legacy.F90 | elpa
 	$(call extract_interface,!c>)
 
 test/shared/generated.h: $(wildcard $(top_srcdir)/test/shared/*.*90) | test/shared
@@ -31,3 +27,6 @@ elpa/elpa_generated_fortran_interfaces.h: $(wildcard $(top_srcdir)/src/elpa2/ker
 
 generated_headers= config-f90.h elpa/elpa_generated.h test/shared/generated.h elpa/elpa_generated_fortran_interfaces.h
 generated-headers: $(generated_headers)
+
+
+# vim: syntax=make