test(rules): reproduce #6843 (#6956)

Cross compilation setup causes dune to crash

Signed-off-by: Rudi Grinberg <[email protected]>

test/blackbox-tests/test-cases/custom-cross-compilation/github6843.t

@@ -0,0 +1,29 @@
+Reproduce #6843
+
+Cross compilation setup that causes dune to crash
+
+  $ cat >dune-workspace <<EOF
+  > (lang dune 3.6)
+  > (context (default))
+  > (context
+  >  (default
+  >   (name esperanto)
+  >   (host default)))
+  > EOF
+
+  $ cat >dune-project <<EOF
+  > (lang dune 3.6)
+  > EOF
+  $ cat >dune <<EOF
+  > (executable (name cat))
+  > EOF
+
+  $ export OCAMLFIND_CONF=$PWD/etc/findlib.conf
+  $ mkdir -p etc/findlib.conf.d
+  $ touch etc/findlib.conf etc/findlib.conf.d/esperanto.conf
+  $ dune build -x esperanto ./cat.exe 2>&1 | awk '/I must not/,/Only I will remain/'
+  I must not crash.  Uncertainty is the mind-killer. Exceptions are the
+  little-death that brings total obliteration.  I will fully express my cases. 
+  Execution will pass over me and through me.  And when it has gone past, I
+  will unwind the stack along its path.  Where the cases are handled there will
+  be nothing.  Only I will remain.