Depend on 1.63 and drop build script autodetection (#17)

Debian stable releases in a few days, and has Rust 1.63. Bump the MSRV
to 1.63, and remove the build script autodetection.

.github/workflows/ci.yml

@@ -52,7 +52,7 @@ jobs:
         os: [ubuntu-latest, windows-latest]
         # When updating this, the reminder to update the minimum supported
         # Rust version in Cargo.toml.
-        rust: ['1.48']
+        rust: ['1.63']
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust

Cargo.toml

@@ -6,7 +6,7 @@ name = "async-fs"
 version = "1.6.0"
 authors = ["Stjepan Glavina <[email protected]>"]
 edition = "2018"
-rust-version = "1.48"
+rust-version = "1.63"
 description = "Async filesystem primitives"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/async-fs"

src/lib.rs

@@ -1091,28 +1091,28 @@ impl std::os::windows::io::AsRawHandle for File {
     }
 }
 
-#[cfg(all(not(async_fs_no_io_safety), unix))]
+#[cfg(unix)]
 impl From<std::os::unix::io::OwnedFd> for File {
     fn from(fd: std::os::unix::io::OwnedFd) -> Self {
         File::from(std::fs::File::from(fd))
     }
 }
 
-#[cfg(all(not(async_fs_no_io_safety), windows))]
+#[cfg(windows)]
 impl From<std::os::windows::io::OwnedHandle> for File {
     fn from(fd: std::os::windows::io::OwnedHandle) -> Self {
         File::from(std::fs::File::from(fd))
     }
 }
 
-#[cfg(all(not(async_fs_no_io_safety), unix))]
+#[cfg(unix)]
 impl std::os::unix::io::AsFd for File {
     fn as_fd(&self) -> std::os::unix::io::BorrowedFd<'_> {
         self.file.as_fd()
     }
 }
 
-#[cfg(all(not(async_fs_no_io_safety), windows))]
+#[cfg(windows)]
 impl std::os::windows::io::AsHandle for File {
     fn as_handle(&self) -> std::os::windows::io::BorrowedHandle<'_> {
         self.file.as_handle()