bitset, nonblocking-* tests: Fix gcc -Wunused-but-set-variable warnings

[Bruno Haible]

I've seen these two warnings more than once:

test-bitset.c:277:19: warning: variable 'i' set but not used 
[-Wunused-but-set-variable]
test-nonblocking-misc.h:101:10: warning: variable 'spent_time' set but not used 
[-Wunused-but-set-variable]

Time to fix them...


2023-09-04  Bruno Haible  <bruno@clisp.org>

        bitset, nonblocking-* tests: Fix gcc -Wunused-but-set-variable warnings.
        * tests/test-bitset.c (check_zero): Mark 'i' as possibly unused.
        * tests/test-nonblocking-reader.h (full_read): Mark 'spent_time' as
        possibly unused.

diff --git a/tests/test-bitset.c b/tests/test-bitset.c
index 8c1d6aee7b..b1250d53fe 100644
--- a/tests/test-bitset.c
+++ b/tests/test-bitset.c
@@ -274,7 +274,7 @@ check_zero (bitset bs)
   /* FOR_EACH.  */
   {
     bitset_iterator iter;
-    bitset_bindex i;
+    _GL_UNUSED bitset_bindex i;
     BITSET_FOR_EACH (iter, bs, i, 0)
       ASSERT (0);
     BITSET_FOR_EACH_REVERSE (iter, bs, i, 0)
diff --git a/tests/test-nonblocking-reader.h b/tests/test-nonblocking-reader.h
index e6f7a3da45..e9076497d4 100644
--- a/tests/test-nonblocking-reader.h
+++ b/tests/test-nonblocking-reader.h
@@ -74,6 +74,7 @@ full_read (size_t fd, void *buf, size_t count)
       END_TIMING
       dbgfprintf (stderr, "%s: << read -> %ld%s\n", PROG_ROLE,
                   (long) ret, dbgstrerror (ret < 0, saved_errno));
+      (void) spent_time;
       if (ret < 0)
         return -1;
       else