This is a temporary patch to eliminate two failures of grep invocation. An
upstream bug was created.

https://sourceforge.net/p/gnuplot/bugs/2806/
--- gnuplot-6.0.3/docs/Makefile.am
+++ gnuplot-6.0.3/docs/Makefile.am
@@ -133,7 +133,7 @@
 endif
 
 allterm.h: $(CORETERM) $(LUA_HELP)
-	$(AM_V_GEN) for e in `grep -E "^[ 	]*START_HELP" $(CORETERM) |\
+	$(AM_V_GEN) for e in `egrep "^[ 	]*START_HELP" $(CORETERM) |\
 	     LC_ALL=C sort -f -t':' -k2` ; do \
 	  f=`echo $$e |cut -d\: -f1` ; s=`echo $$e | cut -d\: -f2` ;\
 	  sed -n "/^[ 	]*$$s/,/^[ 	]*END_HELP/p" $$f ; \
@@ -243,7 +243,7 @@
 	cp $(top_srcdir)/docs/term-ja.diff ja
 	cp -r $(top_srcdir)/term $(TJ)
 	-( cd ja ; patch -p0 < term-ja.diff )
-	$(AM_V_GEN) for e in `grep -E "^[ 	]*START_HELP" $(JATERM) |\
+	$(AM_V_GEN) for e in `egrep "^[ 	]*START_HELP" $(JATERM) |\
 	     LC_ALL=C sort -f -t':' -k2` ; do \
 	  f=`echo $$e |cut -d\: -f1` ; s=`echo $$e | cut -d\: -f2` ;\
 	  LC_ALL=C sed -n "/^[ 	]*$$s/,/^[ 	]*END_HELP/p" $$f ; \