gdb/solib-target: move make_target_solib_ops out of HAVE_LIBEXPAT

When building without expat, we get a missing make_target_solib_ops
error:

    /usr/bin/ld: arch-utils.o: in function `gdbarch::gdbarch()':
    /home/simark/src/binutils-gdb/gdb/gdbarch-gen.c:30:(.text+0x15be): undefined reference to `make_target_solib_ops()'

Fix it by moving make_target_solib_ops out of HAVE_LIBEXPAT.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33118
Change-Id: I76fe4698c6b71bd76096e6cdcbacf8de42a3eb43
Tested-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
diff --git a/gdb/solib-target.c b/gdb/solib-target.c
index 4f0c0ec..770028d 100644
--- a/gdb/solib-target.c
+++ b/gdb/solib-target.c
@@ -209,14 +209,6 @@ static const struct gdb_xml_element library_list_elements[] = {
   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 };
 
-/* See solib-target.h.  */
-
-solib_ops_up
-make_target_solib_ops ()
-{
-  return std::make_unique<target_solib_ops> ();
-}
-
 static std::vector<lm_info_target_up>
 solib_target_parse_libraries (const char *library)
 {
@@ -393,3 +385,11 @@ target_solib_ops::in_dynsym_resolve_code (CORE_ADDR pc) const
      PLT entries (which may be import stubs).  */
   return in_plt_section (pc);
 }
+
+/* See solib-target.h.  */
+
+solib_ops_up
+make_target_solib_ops ()
+{
+  return std::make_unique<target_solib_ops> ();
+}