devel/php*-intl: unbreak build with ICU 75

In file included from ext/intl/intl_convertcpp.cpp:17:
In file included from ./intl_convertcpp.h:22:
In file included from /usr/local/include/unicode/unistr.h:39:
/usr/local/include/unicode/stringpiece.h:133:29: error: no template named 'enable_if_t' in namespace 'std'

typename = std::enable_if_t<
           ~~~~~^

/usr/local/include/unicode/stringpiece.h:134:23: error: no template named 'is_same_v' in namespace 'std'; did you mean 'is_same'?

(std::is_same_v<decltype(T().data()), const char*>
 ~~~~~^

/usr/include/c++/v1/__type_traits/is_same.h:22:29: note: 'is_same' declared here
struct _LIBCPP_TEMPLATE_VIS is_same : _BoolConstant<__is_same(_Tp, _Up)> { };

^

In file included from ext/intl/intl_convertcpp.cpp:17:
In file included from ./intl_convertcpp.h:22:
In file included from /usr/local/include/unicode/unistr.h:39:
/usr/local/include/unicode/stringpiece.h:139:17: error: use of address-of-label extension outside of a function body

std::is_same_v<decltype(T().size()), size_t>>>
^

/usr/local/include/unicode/stringpiece.h:139:62: error: expected member name or ';' after declaration specifiers

std::is_same_v<decltype(T().size()), size_t>>>
                                             ^

PR: 278420
Reported by: antoine (via exp-run)