Makefile: add dependency on external header versions.

There were a few reports that upgrading Ubuntu recently caused issues
because we assert that the sqlite3 library version matches the one we
were built with. 'make' doesn't fix this, because it doesn't know the
external libraries have changed.

Fix this harder, with a helper which updates a file every binary depends
on, which gets relinked every time so we detect link changes.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tools/headerversions.c

@@ -0,0 +1,47 @@
+/* Updates the given file if any library versions have changed.  This
+ * is important for systemwide updates, such as sqlite3. */
+#include <ccan/err/err.h>
+#include <ccan/read_write_all/read_write_all.h>
+#include <ccan/tal/grab_file/grab_file.h>
+#include <ccan/tal/str/str.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <gmp.h>
+#include <sqlite3.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <zlib.h>
+
+int main(int argc, char *argv[])
+{
+	char *file, *new;
+
+	err_set_progname(argv[0]);
+
+	if (argc != 2)
+		errx(1, "Usage: %s <versionheader>", argv[0]);
+
+	file = grab_file(NULL, argv[1]);
+	if (!file && errno != ENOENT)
+		err(1, "Reading %s", argv[1]);
+
+	new = tal_fmt(NULL,
+		      "/* Generated file by tools/headerversions, do not edit! */\n"
+		      "/* GMP version: %s */\n"
+		      "/* SQLITE3 version: %u */\n"
+		      "/* ZLIB version: %s */\n",
+		      gmp_version,
+		      sqlite3_libversion_number(),
+		      zlibVersion());
+	if (!file || !streq(new, file)) {
+		int fd = open(argv[1], O_TRUNC|O_WRONLY|O_CREAT, 0666);
+		if (fd < 0)
+			err(1, "Writing %s", argv[1]);
+		if (!write_all(fd, new, strlen(new)))
+			err(1, "Writing to %s", argv[1]);
+		close(fd);
+	}
+	tal_free(new);
+	tal_free(file);
+	return 0;
+}