debuggers: make the test safe to build without dlopen

This is a bit of overkill, but I'm cleaning out a bunch of other
libltdl-support assumptions, so I might as well do this one, too.  The
test isn't built if we don't have libltdl support, but it had
half-hearted #if protection in it to make it safe to build even if we
didn't have libltdl support.  This commit finishes that half-hearted
support.

ompi/debuggers/Makefile.am

@@ -44,6 +44,7 @@ headers = \
         msgq_interface.h ompi_msgq_dll_defs.h
 
 # Simple checks to ensure that the DSOs are functional
+# This test is only built if we have libltdl support.
 
 dlopen_test_SOURCES = dlopen_test.c
 dlopen_test_CPPFLAGS = -I$(top_srcdir)/opal/libltdl

ompi/debuggers/dlopen_test.c

@@ -15,19 +15,16 @@
 
 #include "opal/libltdl/ltdl.h"
 
-static int do_test(void);
-
+#if !OPAL_WANT_LIBLTDL
 int main(int argc, char *argv[])
 {
-#if OPAL_WANT_LIBLTDL
-    return do_test();
-#else
     /* If OPAL wasn't built with libltdl support, then skip this test */
     fprintf(stderr, "OPAL was not built with libltdl support; skipping\n");
     return 77;
-#endif
 }
 
+#else /* OPAL_WANT_LIBLTDL */
+
 static int do_test(void)
 {
     FILE *fp;
@@ -128,3 +125,9 @@ static int do_test(void)
 
     return 2;
 }
+
+int main(int argc, char *argv[])
+{
+    return do_test();
+}
+#endif /* OPAL_WANT_LIBLTDL */