Stop linking against libflatpak

The configure check for flatpak was a leftover from
when we stopped linking our tests against libflatpak.
We should not bring this back for the main binary.
Instead, ship a standalone copy of FlatpakInstance,
and use that.

configure.ac

@@ -61,7 +61,7 @@ AC_PATH_PROG([BWRAP], [bwrap])
 AC_SUBST([GLIB_COMPILE_RESOURCES], [`$PKG_CONFIG --variable glib_compile_resources gio-2.0`])
 AC_SUBST([GDBUS_CODEGEN], [`$PKG_CONFIG --variable gdbus_codegen gio-2.0`])
 
-PKG_CHECK_MODULES(BASE, [glib-2.0 gio-2.0 gio-unix-2.0 fontconfig])
+PKG_CHECK_MODULES(BASE, [glib-2.0 gio-2.0 gio-unix-2.0 fontconfig json-glib-1.0])
 AC_SUBST(BASE_CFLAGS)
 AC_SUBST(BASE_LIBS)
 
@@ -136,7 +136,6 @@ fi
 GLIB_TESTS
 
 PKG_CHECK_MODULES(FUSE, [fuse])
-PKG_CHECK_MODULES(FLATPAK, [flatpak])
 
 AC_CONFIG_FILES([
 Makefile

src/Makefile.am.inc

@@ -151,6 +151,8 @@ xdg_desktop_portal_SOURCES = \
 	src/fc-monitor.h		\
 	src/background.c		\
 	src/background.h		\
+        src/flatpak-instance.c          \
+        src/flatpak-instance.h          \
 	$(NULL)
 
 if HAVE_PIPEWIRE
@@ -175,7 +177,6 @@ xdg_desktop_portal_LDADD = \
 	$(BASE_LIBS) \
 	$(PIPEWIRE_LIBS) \
 	$(GEOCLUE_LIBS) \
-        $(FLATPAK_LIBS) \
 	$(NULL)
 xdg_desktop_portal_CFLAGS = \
 	-DPKGDATADIR=\"$(pkgdatadir)\" \
@@ -184,7 +185,6 @@ xdg_desktop_portal_CFLAGS = \
 	$(BASE_CFLAGS) \
 	$(PIPEWIRE_CFLAGS) \
 	$(GEOCLUE_CFLAGS) \
-        $(FLATPAK_CFLAGS) \
 	-I$(srcdir)/src \
 	-I$(builddir)/src \
 	$(NULL)

src/background.c

@@ -25,13 +25,13 @@
 #include <gio/gio.h>
 #include <gio/gdesktopappinfo.h>
 
-#include <flatpak.h>
 #include "background.h"
 #include "request.h"
 #include "permissions.h"
 #include "xdp-dbus.h"
 #include "xdp-impl-dbus.h"
 #include "xdp-utils.h"
+#include "flatpak-instance.h"
 
 #define PERMISSION_TABLE "background"
 #define PERMISSION_ID "background"