install with piped input fails if target file exists

[edwardpeek-crown-public]

Reproduction steps

$ echo foo | install /dev/stdin bar
$ echo foo | install /dev/stdin bar
install: No such file or directory

Expected behaviour

Piped content is written to target file as per coreutils behaviour, regardless of whether target file exists.

Actual behaviour

Error message printed about missing file only if target file already exists.

From an strace it looks like it trips up chasing symlinks for the stdin pipe:

readlink("/proc", 0x7ffe5f48f540, 1023) = -1 EINVAL (Invalid argument)
readlink("/proc/self", "328710", 1023)  = 6
readlink("/proc/328710", 0x7ffe5f48f540, 1023) = -1 EINVAL (Invalid argument)
readlink("/proc/328710/fd", 0x7ffe5f48f540, 1023) = -1 EINVAL (Invalid argument)
readlink("/proc/328710/fd/0", "pipe:[2063159]", 1023) = 14
readlink("/proc/328710/fd/pipe:[2063159]", 0x7ffe5f48f540, 1023) = -1 ENOENT (No such file or directory)