Revert "Bump bockbuild", as it breaks the build.

This reverts commit 30f9a22f0869d727c663cc4ba2c283ce75dc73f2.

diff --git a/external/bockbuild b/external/bockbuild
index 45aa142fa322f5b41051e7f40008f03346a1e119..c783777342f4d39b58f3c2e6a1659eedf504ac87 160000 (submodule)
--- a/external/bockbuild
+++ b/external/bockbuild
@@ -1 +1 @@
-Subproject commit 45aa142fa322f5b41051e7f40008f03346a1e119
+Subproject commit c783777342f4d39b58f3c2e6a1659eedf504ac87