[ntupleutil] exporter: error out if the output file is not writable #15387

Job	Run time
Windows 10 x64 Release	1h 2m 49s
Windows 10 x86 Release	1h 3m 11s
Upload Event Payload	3s
mac13 ARM64 LLVM_ENABLE_ASSERTIONS=On, builtin_zlib=ON	33m 52s
fedora40 LLVM_ENABLE_ASSERTIONS=On, CMAKE_CXX_STANDARD=20	53m 4s
mac14 X64 LLVM_ENABLE_ASSERTIONS=On, CMAKE_CXX_STANDARD=20	1h 7m 54s
fedora41 LLVM_ENABLE_ASSERTIONS=On	58m 38s
mac15 ARM64 LLVM_ENABLE_ASSERTIONS=On, CMAKE_CXX_STANDARD=20	35m 13s
alma8 LLVM_ENABLE_ASSERTIONS=On	56m 23s
mac-beta ARM64 LLVM_ENABLE_ASSERTIONS=On, CMAKE_CXX_STANDARD=20	50m 41s
alma9 LLVM_ENABLE_ASSERTIONS=On, CMAKE_BUILD_TYPE=Debug	1h 54m 17s
ubuntu22 imt=Off, LLVM_ENABLE_ASSERTIONS=On, CMAKE_BUILD_TYPE=Debug	1h 11m 11s
ubuntu2404 LLVM_ENABLE_ASSERTIONS=On, CMAKE_BUILD_TYPE=Debug	2h 29m 51s
ubuntu2410 LLVM_ENABLE_ASSERTIONS=On, CMAKE_BUILD_TYPE=Debug	1h 54m 44s
debian125 LLVM_ENABLE_ASSERTIONS=On, CMAKE_CXX_STANDARD=20	59m 52s
alma9 modules_off runtime_cxxmodules=Off	35m 36s
alma9 march_native CMAKE_BUILD_TYPE=RelWithDebInfo, CMAKE_CXX_FLAGS=-march=native, CMAKE_C_FLAGS=-march=native, fortran=OFF	15s
alma9 arm64 CMAKE_BUILD_TYPE=RelWithDebInfo	50m 16s
alma9-clang clang LLVM_ENABLE_ASSERTIONS=On, CMAKE_C_COMPILER=clang, CMAKE_CXX_COMPILER=clang++	1h 12m 26s
	19h 10m 16s

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