Rm unused FromEnvErrorKuind::CannotSetNonBlocking

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

Author: NobodyXu

src/error.rs

@@ -28,8 +28,6 @@ pub enum FromEnvErrorKind {
     CannotOpenPath,
     /// Cannot open file descriptor from the jobserver environment variable value.
     CannotOpenFd,
-    /// Cannot set file descriptor to non blocking
-    CannotSetNonBlocking,
     /// The jobserver style is a simple pipe, but at least one of the file descriptors
     /// is negative, which means it is disabled for this process
     /// ([GNU `make` manual: POSIX Jobserver Interaction](https://www.gnu.org/software/make/manual/make.html#POSIX-Jobserver)).
@@ -49,7 +47,6 @@ impl FromEnvError {
             FromEnvErrorInner::CannotParse(_) => FromEnvErrorKind::CannotParse,
             FromEnvErrorInner::CannotOpenPath(..) => FromEnvErrorKind::CannotOpenPath,
             FromEnvErrorInner::CannotOpenFd(..) => FromEnvErrorKind::CannotOpenFd,
-            FromEnvErrorInner::CannotSetNonBlocking(..) => FromEnvErrorKind::CannotSetNonBlocking,
             FromEnvErrorInner::NegativeFd(..) => FromEnvErrorKind::NegativeFd,
             FromEnvErrorInner::NotAPipe(..) => FromEnvErrorKind::NotAPipe,
             FromEnvErrorInner::Unsupported => FromEnvErrorKind::Unsupported,
@@ -65,7 +62,6 @@ impl std::fmt::Display for FromEnvError {
             FromEnvErrorInner::CannotParse(s) => write!(f, "cannot parse jobserver environment variable value: {s}"),
             FromEnvErrorInner::CannotOpenPath(s, err) => write!(f, "cannot open path or name {s} from the jobserver environment variable value: {err}"),
             FromEnvErrorInner::CannotOpenFd(fd, err) => write!(f, "cannot open file descriptor {fd} from the jobserver environment variable value: {err}"),
-            FromEnvErrorInner::CannotSetNonBlocking(fd, err) => write!(f, "cannot set file descriptor {fd} to be non-blocking: {err}"),
             FromEnvErrorInner::NegativeFd(fd) => write!(f, "file descriptor {fd} from the jobserver environment variable value is negative"),
             FromEnvErrorInner::NotAPipe(fd, None) => write!(f, "file descriptor {fd} from the jobserver environment variable value is not a pipe"),
             FromEnvErrorInner::NotAPipe(fd, Some(err)) => write!(f, "file descriptor {fd} from the jobserver environment variable value is not a pipe: {err}"),
@@ -93,7 +89,6 @@ pub(crate) enum FromEnvErrorInner {
     CannotParse(String),
     CannotOpenPath(String, std::io::Error),
     CannotOpenFd(RawFd, std::io::Error),
-    CannotSetNonBlocking(RawFd, std::io::Error),
     NegativeFd(RawFd),
     NotAPipe(RawFd, Option<std::io::Error>),
     Unsupported,