[D] Fix failing EH execution test on i386.
Turn off partitioning unless it was explicitly requested, as it doesn't
work with D exception chaining, where personality routines use LSDA to
determine whether two thrown exceptions are in the same context.
The following distills what was failing in the D testsuite.
```
try {
try {
fn(); // throws "1"
}
finally {
throw new Exception("2");
}
}
catch (Exception e) {
assert(e.msg == "1");
assert(e.next.msg == "2");
}
```
gcc/d/ChangeLog:
PR d/87824
* d-lang.cc (d_post_options): Disable implicit
-forder-blocks-and-partition.
From-SVN: r267985