gh-108494: Don't build _testclinic_limited with TraceRefs

[vstinner]

If Python is built with ./configure --with-trace-refs, don't build the _testclinic_limited extension. The limited C API (Py_LIMITED_API) is not compatible with Py_TRACE_REFS.

• Issue: Add support for the limited C API to Argument Clinic #108494

[vstinner]

Currently, building Python on the TraceRefs buildbot fails with:

gcc  -fno-strict-overflow -Wsign-compare -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -g -Og -Wall    -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal  -I. -I./Include    -fPIC -c ./Modules/_testclinic_limited.c -o Modules/_testclinic_limited.o
In file included from ./Include/Python.h:44,
                 from ./Modules/_testclinic_limited.c:7:
./Include/object.h:62:4: error: #error Py_LIMITED_API is incompatible with Py_TRACE_REFS
   62 | #  error Py_LIMITED_API is incompatible with Py_TRACE_REFS
      |    ^~~~~
make: *** [Makefile:3139: Modules/_testclinic_limited.o] Error 1

link: https://buildbot.python.org/all/#/builders/484/builds/3914

You can reproduce with:

make distclean
./configure --with-pydebug --with-trace-refs && make

With this change, the build completes as expected and test_clinic pass:

$ make && ./python -m test -v test_clinic 

The following modules are *disabled* in configure script:
_testclinic_limited   xxlimited             xxlimited_35       

(...)
test_my_int_func (test.test_clinic.LimitedCAPIFunctionalTest.test_my_int_func) ... skipped '_testclinic_limited is missing'
test_my_int_sum (test.test_clinic.LimitedCAPIFunctionalTest.test_my_int_sum) ... skipped '_testclinic_limited is missing'
(...)

[vstinner]

cc @erlend-aasland

[vstinner]

Merged, thanks for the review.