delete wasi truncation_rights test (#6236)

This test was not meaningfully executing, because wasi-common never
provides rights containing RIGHTS_PATH_FILESTAT_SET_SIZE - this flag is
not even defined in wasi-common/srd/dir.rs as one of the DirCaps flags.

Even when you get rid of that guard that skips the meat of the test,
path_open was being called with OFLAGS_TRUNC but without
RIGHTS_FD_WRITE, which boils down to an `open(2)` with OFLAGS_TRUNC set
and none of the access modes set, so it will always fail with EINVAL.

So, it doesn't look like this test ever would have meaningfully passed,
even in pre-wiggle-rewrite version of wasi-common it landed in back in
late 2019. Late 2019! before the pandemic! our eyes were so full of
stars and dreams of the future!

The behavior we really care about for truncation are taken care of
by the fd_filestat_set test, which shows fd_filestat_set_size works
correctly, and the file_truncation test, which shows that opening
with OFLAGS_TRUNC will truncate the file.

crates/test-programs/wasi-tests/src/bin/truncation_rights.rs

@@ -1,98 +0,0 @@
-use std::{env, process};
-use wasi_tests::{assert_errno, create_file, open_scratch_directory};
-
-unsafe fn test_truncation_rights(dir_fd: wasi::Fd) {
-    // Create a file in the scratch directory.
-    create_file(dir_fd, "file");
-
-    // Get the rights for the scratch directory.
-    let mut dir_fdstat =
-        wasi::fd_fdstat_get(dir_fd).expect("calling fd_fdstat on the scratch directory");
-    assert_eq!(
-        dir_fdstat.fs_filetype,
-        wasi::FILETYPE_DIRECTORY,
-        "expected the scratch directory to be a directory",
-    );
-    assert_eq!(
-        dir_fdstat.fs_flags, 0,
-        "expected the scratch directory to have no special flags",
-    );
-    assert_eq!(
-        dir_fdstat.fs_rights_base & wasi::RIGHTS_FD_FILESTAT_SET_SIZE,
-        0,
-        "directories shouldn't have the fd_filestat_set_size right",
-    );
-
-    // If we have the right to set sizes from paths, test that it works.
-    if (dir_fdstat.fs_rights_base & wasi::RIGHTS_PATH_FILESTAT_SET_SIZE) == 0 {
-        eprintln!("implementation doesn't support setting file sizes, skipping");
-    } else {
-        // Test that we can truncate the file.
-        let mut file_fd = wasi::path_open(dir_fd, 0, "file", wasi::OFLAGS_TRUNC, 0, 0, 0)
-            .expect("truncating a file");
-        wasi::fd_close(file_fd).expect("closing a file");
-
-        let mut rights_base: wasi::Rights = dir_fdstat.fs_rights_base;
-        let mut rights_inheriting: wasi::Rights = dir_fdstat.fs_rights_inheriting;
-
-        if (rights_inheriting & wasi::RIGHTS_FD_FILESTAT_SET_SIZE) == 0 {
-            eprintln!("implementation doesn't support setting file sizes through file descriptors, skipping");
-        } else {
-            rights_inheriting &= !wasi::RIGHTS_FD_FILESTAT_SET_SIZE;
-            wasi::fd_fdstat_set_rights(dir_fd, rights_base, rights_inheriting)
-                .expect("droping fd_filestat_set_size inheriting right on a directory");
-        }
-
-        // Test that we can truncate the file without the
-        // wasi_unstable::RIGHT_FD_FILESTAT_SET_SIZE right.
-        file_fd = wasi::path_open(dir_fd, 0, "file", wasi::OFLAGS_TRUNC, 0, 0, 0)
-            .expect("truncating a file without fd_filestat_set_size right");
-        wasi::fd_close(file_fd).expect("closing a file");
-
-        rights_base &= !wasi::RIGHTS_PATH_FILESTAT_SET_SIZE;
-        wasi::fd_fdstat_set_rights(dir_fd, rights_base, rights_inheriting)
-            .expect("droping path_filestat_set_size base right on a directory");
-
-        // Test that clearing wasi_unstable::RIGHT_PATH_FILESTAT_SET_SIZE actually
-        // took effect.
-        dir_fdstat = wasi::fd_fdstat_get(dir_fd).expect("reading the fdstat from a directory");
-        assert_eq!(
-            (dir_fdstat.fs_rights_base & wasi::RIGHTS_PATH_FILESTAT_SET_SIZE),
-            0,
-            "reading the fdstat from a directory",
-        );
-
-        // Test that we can't truncate the file without the
-        // wasi_unstable::RIGHT_PATH_FILESTAT_SET_SIZE right.
-        assert_errno!(
-            wasi::path_open(dir_fd, 0, "file", wasi::OFLAGS_TRUNC, 0, 0, 0)
-                .expect_err("truncating a file without path_filestat_set_size right"),
-            wasi::ERRNO_PERM
-        );
-    }
-
-    wasi::path_unlink_file(dir_fd, "file").expect("removing a file");
-}
-
-fn main() {
-    let mut args = env::args();
-    let prog = args.next().unwrap();
-    let arg = if let Some(arg) = args.next() {
-        arg
-    } else {
-        eprintln!("usage: {} <scratch directory>", prog);
-        process::exit(1);
-    };
-
-    // Open scratch directory
-    let dir_fd = match open_scratch_directory(&arg) {
-        Ok(dir_fd) => dir_fd,
-        Err(err) => {
-            eprintln!("{}", err);
-            process::exit(1)
-        }
-    };
-
-    // Run the tests.
-    unsafe { test_truncation_rights(dir_fd) }
-}