graphics/mupdf: Fix linking with libmupdf.so for third-party ports

libmupdf.so references symbols from libmupdfthird.so but does not
link directly against it.

This is problematic for ports using the --as-needed linker option,
such as graphics/zathura-pdf-mupdf (>= 0.3.3) due to Meson's defaults.
zathura-pdf-mupdf itself does not reference symbols from libmupdfthird.so,
and so despite being included in the linker arguments, libmupdfthird.so
is not actually linked in.

$ zathura --version
error: Could not load plugin '/usr/local/lib/zathura/libpdf-mupdf.so' (/usr/local/lib/libmupdf.so.1.13.0: Undefined symbol "js_tointeger").

This is a consequence of us providing shared libraries in spite of
upstream since r433550 to keep package sizes down, but not properly
understanding the dependency between libmupdfthird and libmupdf.

PR:		232059
Submitted by:	Albert Ou <aou@eecs.berkeley.edu>

graphics/mupdf/Makefile

@@ -4,7 +4,7 @@
 PORTNAME=	mupdf
 PORTVERSION=	1.13.0
 DISTVERSIONSUFFIX=	-source
-PORTREVISION=	2
+PORTREVISION=	3
 PORTEPOCH=	1
 CATEGORIES=	graphics
 MASTER_SITES=	http://www.mupdf.com/downloads/ \

graphics/mupdf/files/patch-Makefile

@@ -15,11 +15,12 @@ $OpenBSD: patch-Makefile,v 1.12 2016/12/12 10:54:39 sthen Exp $
 @@ -344,7 +344,11 @@ THIRD_OBJ := \
  THREAD_OBJ := $(THREAD_OBJ)
  
- $(MUPDF_LIB) : $(MUPDF_OBJ)
-+	$(CC) $(LDFLAGS) -fPIC -shared -Wl,-soname=$@ -o $@ $^ $(LIBS)
+-$(MUPDF_LIB) : $(MUPDF_OBJ)
++$(MUPDF_LIB) : $(MUPDF_OBJ) $(THIRD_LIB)
++	$(CC) $(LDFLAGS) -fPIC -shared -Wl,-soname=$@ -Wl,--no-undefined -o $@ $^ $(LIBS)
 +
  $(THIRD_LIB) : $(THIRD_OBJ)
-+	$(CC) $(LDFLAGS) -fPIC -shared -Wl,-soname=$@ -o $@ $^ $(LIBS)
++	$(CC) $(LDFLAGS) -fPIC -shared -Wl,-soname=$@ -Wl,--no-undefined -o $@ $^ $(LIBS)
 +
  $(THREAD_LIB) : $(THREAD_OBJ)