compat: die when unable to set core.precomposeunicode

When calling `git_config_set` to set 'core.precomposeunicode' we
ignore the return value of the function, which may indicate that
we were unable to write the value back to disk. As the function
is only called by init-db we can and should die when an error
occurs.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/precompose_utf8.c

@@ -50,7 +50,8 @@ void probe_utf8_pathname_composition(void)
 		close(output_fd);
 		git_path_buf(&path, "%s", auml_nfd);
 		precomposed_unicode = access(path.buf, R_OK) ? 0 : 1;
-		git_config_set("core.precomposeunicode", precomposed_unicode ? "true" : "false");
+		git_config_set_or_die("core.precomposeunicode",
+				      precomposed_unicode ? "true" : "false");
 		git_path_buf(&path, "%s", auml_nfc);
 		if (unlink(path.buf))
 			die_errno(_("failed to unlink '%s'"), path.buf);