2025.10.06 FTBFS on clang-x86_64: reference to overloaded function could not be resolved

Version: folly 2025.10.06.00

Using clang++-21.1.2 on openSUSE Tumbleweed 20251006 amd64 leads to a build failure:

```
[ 18s] /usr/bin/clang++ -DBOOST_ATOMIC_DYN_LINK -DBOOST_ATOMIC_NO_LIB -DBOOST_CHRONO_DYN_LINK -DBOOST_CHRONO_NO_LIB -DBOOST_CONTAINER_DYN_LINK -DBOOST_CONTAINER_NO_LIB -DBOOST_CONTEXT_DYN_LINK -DBOOST_CONTEXT_NO_LIB -DBOOST_DATE_TIME_DYN_LINK -DBOOST_DATE_TIME_NO_LIB -DBOOST_FILESYSTEM_DYN_LINK -DBOOST_FILESYSTEM_NO_LIB -DBOOST_PROGRAM_OPTIONS_DYN_LINK -DBOOST_PROGRAM_OPTIONS_NO_LIB -DBOOST_REGEX_DYN_LINK -DBOOST_REGEX_NO_LIB -DBOOST_THREAD_DYN_LINK -DBOOST_THREAD_NO_LIB -DFMT_SHARED -DFOLLY_XLOG_STRIP_PREFIXES=\"/home/abuild/rpmbuild/BUILD/folly-2025.10.06.00-build/folly-2025.10.06.00:/home/abuild/rpmbuild/BUILD/folly-2025.10.06.00-build/folly-2025.10.06.00/build\" -DGFLAGS_IS_A_DLL=0 -DGLOG_USE_GLOG_EXPORT=1 -DGOOGLE_GLOG_IS_A_DLL=1 -D_GNU_SOURCE -D_REENTRANT -I/home/abuild/rpmbuild/BUILD/folly-2025.10.06.00-build/folly-2025.10.06.00 -I/home/abuild/rpmbuild/BUILD/folly-2025.10.06.00-build/folly-2025.10.06.00/build -O2 -Wall -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -Werror=return-type -g -ffat-lto-objects -fPIC -O2 -g -DNDEBUG -std=gnu++20 -fPIC -g -finput-charset=UTF-8 -fsigned-char -Wall -Wno-deprecated -Wno-deprecated-declarations -Wno-sign-compare -Wno-unused -Wuninitialized -Wunused-label -Wunused-result -Wno-noexcept-type -Wno-nullability-completeness -Wno-inconsistent-missing-override -faligned-new -fopenmp -MD -MT CMakeFiles/folly_base.dir/folly/Subprocess.cpp.o -MF CMakeFiles/folly_base.dir/folly/Subprocess.cpp.o.d -o CMakeFiles/folly_base.dir/folly/Subprocess.cpp.o -c /home/abuild/rpmbuild/BUILD/folly-2025.10.06.00-build/folly-2025.10.06.00/folly/Subprocess.cpp
[ 18s] /home/abuild/rpmbuild/BUILD/folly-2025.10.06.00-build/folly-2025.10.06.00/folly/Subprocess.cpp:173:34: error: reference to overloaded function could not be resolved; did you mean to call it?
[ 18s] 173 | FOLLY_DETAIL_SUBPROCESS_LIBC_X(FOLLY_DETAIL_SUBPROCESS_LIBC_FIELD_DECL)
[ 18s] | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[ 18s] /home/abuild/rpmbuild/BUILD/folly-2025.10.06.00-build/folly-2025.10.06.00/folly/Subprocess.cpp:162:39: note: expanded from macro 'FOLLY_DETAIL_SUBPROCESS_LIBC_X'
[ 18s] 162 | FOLLY_DETAIL_SUBPROCESS_LIBC_X_OPEN(X) \
[ 18s] | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
[ 18s] /home/abuild/rpmbuild/BUILD/folly-2025.10.06.00-build/folly-2025.10.06.00/folly/Subprocess.cpp:151:3: note: expanded from macro 'FOLLY_DETAIL_SUBPROCESS_LIBC_X_OPEN'
[ 18s] 151 | X(openat, openat)
[ 18s] | ^~~~~~~~~~~~~~~~~
[ 18s] /home/abuild/rpmbuild/BUILD/folly-2025.10.06.00-build/folly-2025.10.06.00/folly/Subprocess.cpp:166:19: note: expanded from macro 'FOLLY_DETAIL_SUBPROCESS_LIBC_FIELD_DECL'
[ 18s] 166 | static decltype(&::func) name;
[ 18s] | ^~~~~~~
```