Without stack protector, inhibit_stack_protector is undefined during build:

In file included from <command-line>:
./../include/libc-symbols.h:665:3: error: expected ';' before '__typeof'
  665 |   __typeof (type_name) *name##_ifunc (__VA_ARGS__)
         \
      |   ^~~~~~~~
./../include/libc-symbols.h:676:3: note: in expansion of macro
'__ifunc_resolver'
  676 |   __ifunc_resolver (type_name, name, expr, init, static, __VA_ARGS__)
      |   ^~~~~~~~~~~~~~~~
./../include/libc-symbols.h:703:3: note: in expansion of macro '__ifunc_args'
  703 |   __ifunc_args (type_name, name, expr, init, arg)
      |   ^~~~~~~~~~~~
./../include/libc-symbols.h:790:3: note: in expansion of macro '__ifunc'
  790 |   __ifunc (redirected_name, name, expr, void, INIT_ARCH)
      |   ^~~~~~~
../sysdeps/x86_64/multiarch/memchr.c:29:1: note: in expansion of macro
'libc_ifunc_redirected'
   29 | libc_ifunc_redirected (__redirect_memchr, memchr, IFUNC_SELECTOR ());
      | ^~~~~~~~~~~~~~~~~~~~~

1. Fix a typo in include/libc-symbols.h to define inhibit_stack_protector
for build.
2. Don't include <config.h> in include/libc-symbols.h since it has been
included in include/libc-misc.h.
3. Change #include "libc-misc.h" to #include <libc-misc.h> in
string/test-string.h.

This fixes BZ #32494.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>

Add include/libc-misc.h to provide miscellaneous definitions for both
glibc build and test:

1. Move inhibit_stack_protector to libc-misc.h and add Clang support.
2. Add test_inhibit_stack_protector for glibc testing.
3. Move inhibit_loop_to_libcall to libc-misc.h.
4. Add test_cc_inhibit_loop_to_libcall to handle TEST_CC != CC and
replace inhibit_loop_to_libcall with test_cc_inhibit_loop_to_libcall
in glibc tests.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Co-Authored-By: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Sam James <sam@gentoo.org>