bpo-36301: Fix _PyPreConfig_Read() compiler warning

[vstinner]

Initialize init_utf8_mode earlier to fix a compiler warning.

https://bugs.python.org/issue36301

[vstinner]

Example of warning seen on PR #12661:

https://dev.azure.com/Python/cpython/_build/results?buildId=40348

Python/preconfig.c:725:13: warning: variable 'init_utf8_mode' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
        if (_Py_INIT_FAILED(err)) {
            ^~~~~~~~~~~~~~~~~~~~
./Include/cpython/coreconfig.h:37:5: note: expanded from macro '_Py_INIT_FAILED'
    (err.msg != NULL || err.exitcode != -1)
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Python/preconfig.c:815:19: note: uninitialized use occurs here
    Py_UTF8Mode = init_utf8_mode ;
                  ^~~~~~~~~~~~~~
Python/preconfig.c:725:9: note: remove the 'if' if its condition is always false
        if (_Py_INIT_FAILED(err)) {
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~
Python/preconfig.c:725:29: warning: variable 'init_utf8_mode' is used uninitialized whenever '||' condition is true [-Wsometimes-uninitialized]
        if (_Py_INIT_FAILED(err)) {
            ~~~~~~~~~~~~~~~~^~~~
./Include/cpython/coreconfig.h:37:6: note: expanded from macro '_Py_INIT_FAILED'
    (err.msg != NULL || err.exitcode != -1)
     ^~~~~~~~~~~~~~~
Python/preconfig.c:815:19: note: uninitialized use occurs here
    Py_UTF8Mode = init_utf8_mode ;
                  ^~~~~~~~~~~~~~
Python/preconfig.c:725:29: note: remove the '||' if its condition is always false
        if (_Py_INIT_FAILED(err)) {
                            ^
Python/preconfig.c:730:5: note: variable 'init_utf8_mode' is declared here
    int init_utf8_mode = Py_UTF8Mode;
    ^
2 warnings generated.

[tirkarthi]

See also #12644 . Does this PR also fix the same issue ?

[vstinner]

See also #12644 . Does this PR also fix the same issue ?

Thanks. I missed this PR, thanks for the pointer. I closed this PR as well.