Add BWRAP and --with-system-bubblewrap configure arguments

This lets distributors share a system copy of bubblewrap (>= 0.1.0)
between Flatpak and any other projects that benefit from it, if they are
careful to keep new versions in sync. The default is still to use the
bundled submodule, ensuring compatibility and simplifying dependencies.

Enable $PATH search everywhere that runs bwrap, so that $BWRAP doesn't
necessarily need to be a fully-qualified path.

Signed-off-by: Simon McVittie <smcv@debian.org>

Makefile.am

@@ -41,7 +41,6 @@ AM_CPPFLAGS =							\
 	-DFLATPAK_BASEDIR=\"$(pkgdatadir)\"			\
 	-DFLATPAK_TRIGGERDIR=\"$(pkgdatadir)/triggers\"		\
 	-DSYSTEM_FONTS_DIR=\"$(SYSTEM_FONTS_DIR)\"		\
-	-DHELPER=\"$(libexecdir)/flatpak-bwrap\"		\
 	-DDBUSPROXY=\"$(libexecdir)/flatpak-dbus-proxy\"	\
 	-DG_LOG_DOMAIN=\"flatpak\"				\
 	-I$(srcdir)/libglnx					\
@@ -49,6 +48,12 @@ AM_CPPFLAGS =							\
 	-I$(builddir)/common					\
 	$(NULL)
 
+if WITH_SYSTEM_BWRAP
+AM_CPPFLAGS += -DHELPER=\"$(BWRAP)\"
+else
+AM_CPPFLAGS += -DHELPER=\"$(libexecdir)/flatpak-bwrap\"
+endif
+
 triggersdir = $(pkgdatadir)/triggers
 dist_triggers_SCRIPTS = \
 	triggers/gtk-icon-cache.trigger \
@@ -79,6 +84,8 @@ include permission-store/Makefile.am.inc
 include document-portal/Makefile.am.inc
 include tests/Makefile.am.inc
 
+if !WITH_SYSTEM_BWRAP
+
 bwrap_PROGRAMS = flatpak-bwrap
 flatpak_bwrap_SOURCES = $(bwrap_SOURCES)
 flatpak_bwrap_CFLAGS = $(bwrap_CFLAGS)
@@ -98,6 +105,8 @@ if PRIV_MODE_FILECAPS
 endif
 endif
 
+endif # !WITH_SYSTEM_BWRAP
+
 completiondir = $(datadir)/bash-completion/completions
 completion_DATA = completion/flatpak
 EXTRA_DIST += $(completion_DATA)

app/flatpak-builtins-build.c

@@ -224,7 +224,7 @@ flatpak_builtin_build (int argc, char **argv, GCancellable *cancellable, GError
 
   g_ptr_array_add (argv_array, NULL);
 
-  if (execve (flatpak_get_bwrap (), (char **) argv_array->pdata, envp) == -1)
+  if (execvpe (flatpak_get_bwrap (), (char **) argv_array->pdata, envp) == -1)
     {
       g_set_error (error, G_IO_ERROR, g_io_error_from_errno (errno), "Unable to start app");
       return FALSE;

common/flatpak-dir.c

@@ -2004,7 +2004,7 @@ flatpak_dir_run_triggers (FlatpakDir   *self,
           if (!g_spawn_sync ("/",
                              (char **) argv_array->pdata,
                              NULL,
-                             G_SPAWN_DEFAULT,
+                             G_SPAWN_SEARCH_PATH,
                              NULL, NULL,
                              NULL, NULL,
                              NULL, &trigger_error))

configure.ac

@@ -100,6 +100,20 @@ AC_ARG_WITH(system_fonts_dir,
 SYSTEM_FONTS_DIR=$with_system_fonts_dir
 AC_SUBST(SYSTEM_FONTS_DIR)
 
+AC_ARG_VAR([BWRAP], [Bubblewrap executable])
+AC_ARG_WITH([system-bubblewrap],
+            [AS_HELP_STRING([--with-system-bubblewrap], [Use system bwrap executable [default=check $BWRAP]])],
+            [BWRAP="$withval"],
+            [BWRAP="${BWRAP:-false}"])
+AS_CASE([$BWRAP],
+        [yes],
+            [BWRAP=bwrap],
+        [no],
+            [BWRAP=false],
+        [auto],
+            [AC_CHECK_PROG([BWRAP], [bwrap], [bwrap], [false])])
+AM_CONDITIONAL([WITH_SYSTEM_BWRAP], [test "x$BWRAP" != xfalse])
+
 AC_CHECK_FUNCS(fdwalk)
 
 AC_CHECK_HEADER([sys/xattr.h], [], AC_MSG_ERROR([You must have sys/xattr.h from glibc]))

tests/Makefile.am.inc

@@ -1,12 +1,15 @@
 TESTS_ENVIRONMENT += FLATPAK_TESTS_DEBUG=1 \
 	FLATPAK_TRIGGERSDIR=$$(cd $(top_srcdir) && pwd)/triggers \
-	FLATPAK_BWRAP=$$(cd $(top_builddir) && pwd)/flatpak-bwrap \
 	FLATPAK_DBUSPROXY=$$(cd $(top_builddir) && pwd)/flatpak-dbus-proxy \
 	GI_TYPELIB_PATH=$$(cd $(top_builddir) && pwd) \
 	LD_LIBRARY_PATH=$$(cd $(top_builddir)/.libs && pwd) \
 	PATH=$$(cd $(top_builddir) && pwd):$${PATH} \
 	$(NULL)
 
+if !WITH_SYSTEM_BWRAP
+TESTS_ENVIRONMENT += FLATPAK_BWRAP=$$(cd $(top_builddir) && pwd)/flatpak-bwrap
+endif
+
 testdb_CFLAGS = $(BASE_CFLAGS)
 testdb_LDADD = \
              $(BASE_LIBS) \