Make :open ccall use variadic cconv (#49212)

Author: vchuravy

base/file.jl

@@ -105,7 +105,7 @@ if Sys.iswindows()
     end
 else
     function cd(f::Function, dir::AbstractString)
-        fd = ccall(:open, Int32, (Cstring, Int32), :., 0)
+        fd = ccall(:open, Int32, (Cstring, Int32, UInt32...), :., 0)
         systemerror(:open, fd == -1)
         try
             cd(dir)

test/file.jl

@@ -1253,7 +1253,7 @@ let f = open(file, "w")
     if Sys.iswindows()
         f = RawFD(ccall(:_open, Cint, (Cstring, Cint), file, Base.Filesystem.JL_O_RDONLY))
     else
-        f = RawFD(ccall(:open, Cint, (Cstring, Cint), file, Base.Filesystem.JL_O_RDONLY))
+        f = RawFD(ccall(:open, Cint, (Cstring, Cint, UInt32...), file, Base.Filesystem.JL_O_RDONLY))
     end
     test_LibcFILE(Libc.FILE(f, Libc.modestr(true, false)))
 end

test/testhelpers/FakePTYs.jl

@@ -39,7 +39,7 @@ function open_fake_pty()
         rc = ccall(:unlockpt, Cint, (Cint,), fdm)
         rc != 0 && error("unlockpt")
 
-        fds = ccall(:open, Cint, (Ptr{UInt8}, Cint),
+        fds = ccall(:open, Cint, (Ptr{UInt8}, Cint, UInt32...),
             ccall(:ptsname, Ptr{UInt8}, (Cint,), fdm), O_RDWR | O_NOCTTY)
         pts = RawFD(fds)