[libc++] Fix input-only range handling for `vector` #7401

Job	Run time
stage1 (generic-cxx03, clang-19, clang++-19)	7m 49s
stage1 (generic-cxx26, clang-19, clang++-19)	13m 45s
stage1 (generic-modules, clang-19, clang++-19)	10m 34s
stage1 (generic-gcc, gcc-14, g++-14)	20m 1s
macos (generic-cxx03, macos-15)	12m 0s
windows (clang-cl-dll, false)	51m 34s
macos (generic-cxx23, macos-15)	41m 41s
stage2 (generic-cxx11, clang-19, clang++-19)	8m 29s
windows (clang-cl-static, false)	52m 46s
macos (generic-modules, macos-15)	20m 18s
stage2 (generic-cxx14, clang-19, clang++-19)	10m 45s
windows (clang-cl-no-vcruntime, false)	51m 10s
macos (apple-configuration, macos-15)	30m 6s
stage2 (generic-cxx17, clang-19, clang++-19)	10m 54s
windows (clang-cl-debug, false)	50m 45s
macos (apple-system, macos-13)	53m 23s
stage2 (generic-cxx20, clang-19, clang++-19)	15m 16s
windows (clang-cl-static-crt, false)	54m 48s
macos (apple-system-hardened, macos-13)	1h 2m 27s
windows (mingw-dll, true)	1h 11m 14s
stage2 (generic-cxx23, clang-19, clang++-19)	3m 50s
windows (mingw-static, true)	1h 11m 18s
stage2 (generic-gcc-cxx11, gcc-14, g++-14)	11m 12s
stage2 (generic-cxx23, clang-17, clang++-17)	12m 46s
windows (mingw-dll-i686, true)	1h 11m 1s
stage2 (generic-cxx26, clang-18, clang++-18)	16m 20s
windows (mingw-incomplete-sysroot, true)	6m 58s
stage3	0s
	14h 3m 10s

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