`readbytes!(::Process, ::Vector{UInt8}, ::Int)` does not read bytes on 1.11

[iamed2]

On 1.11:

               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.11.0 (2024-10-07)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> function mwe(filepath, nb, max_nb)
           write(filepath, ones(UInt8, nb))
           p = open(`cat $filepath`; read=true)
           b = Vector{UInt8}(undef, 1024)
           nr = readbytes!(p, b, max_nb)
           return nr, b
       end
mwe (generic function with 1 method)

julia> (nr, v) = mwe("/Users/edavies/Downloads/tmp.bin", 53209, typemax(Int))
(53209, UInt8[0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  …  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])

julia> length(v)
1024

On 1.10:

               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.10.5 (2024-08-27)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> function mwe(filepath, nb, max_nb)
           write(filepath, ones(UInt8, nb))
           p = open(`cat $filepath`; read=true)
           b = Vector{UInt8}(undef, 1024)
           nr = readbytes!(p, b, max_nb)
           return nr, b
       end
mwe (generic function with 1 method)

julia> (nr, v) = mwe("/Users/edavies/Downloads/tmp.bin", 53209, typemax(Int))
(53209, UInt8[0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01  …  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])

julia> length(v)
118745

[ararslan]

Same on current master

[nhz2]

Bisected to d7b9ac8 #53192