[tests] disable cache for a few dune commands in cram tests

tests/misc/share_directory.t/run.t

-  $ dune build --root . @install
+  $ dune build --cache=disabled  --root . @install
 
 Basic case
-  $ dune exec -- frama-c
+  $ dune exec --cache=disabled -- frama-c
   [kernel] IS_SET false
   [dirs] path (dir)
   [dirs] Found: FRAMAC_SHARE/dirs/path
@@ -22,7 +22,7 @@ Basic case
 
 With option
   $ cp -r share copied
-  $ dune exec -- frama-c -dirs-share copied
+  $ dune exec --cache=disabled -- frama-c -dirs-share copied
   [kernel] IS_SET true
   [dirs] path (dir)
   [dirs] Found: copied/path

tests/misc/user_directories.unix.t/run.t

@@ -3,7 +3,7 @@ touch the actual user HOME.
 In addition, make sure that you use dune with option `--cache=disabled`,
 in order not to pollute `home/.cache` in dune >= 3.16
 
-  $ dune build --root . @install
+  $ dune build --cache=disabled --root . @install
 
 Basic case
   $ HOME=home dune exec --cache=disabled -- frama-c