[eacsl] Fix tests with `-then`

The option `-machdep` should be called with `-e-acsl-prepare` before the
`-then`, otherwise when `-machdep` is finally used then the project is cleared
and all previous analysis are lost.

src/plugins/e-acsl/tests/memory/local_init.c

 /* run.config_ci
    COMMENT: test of a local initializer which contains an annotation
    LOG: gen_@PTEST_NAME@.c
-   STDOPT: #"-lib-entry -eva -e-acsl-prepare -e-acsl-share ./share/e-acsl -then -no-lib-entry"
+   STDOPT: #"@MACHDEP@ @EACSL_PREPARE@ -lib-entry -eva -then -no-lib-entry"
 */
 
 int X = 0;

src/plugins/e-acsl/tests/special/e-acsl-valid.c

 /* run.config_ci, run.config_dev
    COMMENT: test option -e-acsl-no-valid
-   STDOPT: #"-e-acsl-prepare -e-acsl-share ./share/e-acsl -eva -eva-verbose 0 -then -e-acsl-no-valid"
+   STDOPT: #"@MACHDEP@ @EACSL_PREPARE@ -eva -eva-verbose 0 -then -no-eva -e-acsl-no-valid"
    MACRO: ROOT_EACSL_GCC_FC_EXTRA_EXT -eva -eva-verbose 0
    MACRO: ROOT_EACSL_GCC_OPTS_EXT --then --e-acsl-extra -e-acsl-no-valid
 */

src/plugins/e-acsl/tests/special/oracle_ci/e-acsl-valid.res.oracle

-[eva:alarm] tests/special/e-acsl-valid.c:37: Warning: 
-  function f: precondition \valid(y) got status unknown.
 [eva:alarm] tests/special/e-acsl-valid.c:37: Warning: 
   function f: precondition \valid(y) got status unknown.
 [e-acsl] beginning translation.

src/plugins/e-acsl/tests/test_config_ci.in

 MACRO: DEST @PTEST_RESULT@/gen_@PTEST_NAME@
-MACRO: GLOBAL -machdep gcc_x86_64 -variadic-no-translation -verbose 0
+MACRO: MACHDEP -machdep gcc_x86_64
+MACRO: EACSL_PREPARE -e-acsl-prepare -e-acsl-share ./share/e-acsl
+MACRO: GLOBAL @MACHDEP@ -variadic-no-translation -verbose 0
 MACRO: EACSL -e-acsl -e-acsl-share ./share/e-acsl -e-acsl-verbose 1
 MACRO: EVA -eva -eva-no-alloc-returns-null -eva-no-results -eva-no-print -eva-warn-key libc:unsupported-spec=inactive
 MACRO: EVENTUALLY -print -ocode @DEST@.c -load-script ./tests/print.cmxs