mupdf: fix bug loading mupdf-x11 with shared library build

Error loading shared library build/shared-release/libmupdf.so:
No such file or directory (needed by /bin/mupdf-x11)

caused by a buggy Makefile adding the full path to the .so at link time
instead of -Llocation -lmupdf.

KEEP/mupdf-1.18-shared.patch

@@ -0,0 +1,11 @@
+--- mupdf-1.18.0-source.org/Makefile
++++ mupdf-1.18.0-source/Makefile
+@@ -61,7 +61,7 @@
+ ifdef RANLIB
+   RANLIB_CMD = $(QUIET_RANLIB) $(RANLIB) $@
+ endif
+-LINK_CMD = $(QUIET_LINK) $(MKTGTDIR) ; $(CC) $(LDFLAGS) -o $@ $^ $(LIBS)
++LINK_CMD = $(QUIET_LINK) $(MKTGTDIR) ; $(CC) $(LDFLAGS) -o $@ $(subst $(MUPDF_LIB),-L$(OUT) -lmupdf,$^) $(LIBS)
+ TAGS_CMD = $(QUIET_TAGS) ctags -R --c-kinds=+p
+ WINDRES_CMD = $(QUIET_WINDRES) $(MKTGTDIR) ; $(WINDRES) $< $@
+ OBJCOPY_CMD = $(QUIET_OBJCOPY) $(MKTGTDIR) ; $(LD) -r -b binary -z noexecstack -o $@ $<

pkg/mupdf

@@ -26,6 +26,7 @@ libressl
 jbig2dec
 
 [build]
+patch -p1 < "$K"/mupdf-1.18-shared.patch
 rm -rf thirdparty/curl thirdparty/freetype thirdparty/jpeg thirdparty/zlib thirdparty/jbig2dec
 PCS_SAVE="$PKG_CONFIG_SYSROOT_DIR"
 PCL_SAVE="$PKG_CONFIG_LIBDIR"