[Bug-readline] 8.0-alpha install failure: $(DESTDIR)$(pkgconfigdir) may not exist

[ilove zfs]

Installing into a prefix that doesn't already have the pkgconfig directory existing leads to `make install` failing with the following error:

install: /usr/local/Cellar/readline/8.0-alpha_1/lib/pkgconfig/readline.pc: No such file or directory

I can fix this with the following patch:

https://gist.githubusercontent.com/ilovezfs/96bfc30930c92473f104cf0a9cf9f2e9/raw/ffbb7b7de4aeee7ce978fb33ba6bb8e48bd8aa1e/gistfile1.txt

From b80ca88a0134e244788d0ef330028182dcf6aa5d Mon Sep 17 00:00:00 2001
From: ilovezfs <address@hidden>
Date: Wed, 23 May 2018 00:17:12 -0700
Subject: [PATCH] Make sure pkgconfig directory exists

---
 Makefile.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makefile.in b/Makefile.in
index c7fd8e0..f3a201b 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -260,7 +260,7 @@ install-static: installdirs $(STATIC_LIBS) install-headers install-doc ${install
 
 installdirs: $(srcdir)/support/mkinstalldirs
     -$(SHELL) $(srcdir)/support/mkinstalldirs $(DESTDIR)$(includedir) \
-        $(DESTDIR)$(includedir)/readline $(DESTDIR)$(libdir) \
+        $(DESTDIR)$(includedir)/readline $(DESTDIR)$(libdir) $(DESTDIR)$(pkgconfigdir) \
         $(DESTDIR)$(infodir) $(DESTDIR)$(man3dir) $(DESTDIR)$(docdir)
 
 uninstall: uninstall-headers uninstall-doc uninstall-examples uninstall-pc
--
2.17.0