automake: fix build on centos8

package/automake/patches/patch-Makefile_in

@@ -0,0 +1,11 @@
+--- automake-1.15.1.orig/Makefile.in	2017-06-18 19:35:04.000000000 +0200
++++ automake-1.15.1/Makefile.in	2020-10-31 08:38:23.322590385 +0100
+@@ -710,7 +710,7 @@ update_mans = \
+   $(AM_V_GEN): \
+     && $(MKDIR_P) doc \
+     && $(extend_PATH) \
+-    && $(PERL) $(srcdir)/doc/help2man --output=$@
++    && $(PERL) $(srcdir)/doc/help2man --no-discard-stderr --output=$@
+ 
+ amhello_sources = \
+   doc/amhello/configure.ac \