buildsys: fix build on macOS with libssh2 present via homebrew

Path to libssh2 headers was missing from CPPFLAGS resulting into FTBFS.

Signed-off-by: Yury V. Zaytsev <yury@shurup.com>
Signed-off-by: Andrew Borodin <aborodin@vmail.ru>

src/Makefile.am

@@ -26,6 +26,13 @@ SUBDIRS += consaver
 AM_CPPFLAGS += -DSAVERDIR=\""$(pkglibexecdir)"\"
 endif
 
+# required for textconf.c
+if ENABLE_VFS
+if ENABLE_VFS_SFTP
+AM_CPPFLAGS += $(LIBSSH_CFLAGS)
+endif
+endif
+
 AM_CPPFLAGS += -I$(top_srcdir) $(GLIB_CFLAGS)
 
 localedir = $(datadir)/locale