Fix compilation error on Solaris due to flock usage

PR 130999 added the file_lock feature, but libc does not define
flock() for the Solaris platform leading to a compilation error.

Additionally, I went through all the Tier 2 platforms and read through
their documentation to see whether flock was implemented. This turned up
5 more Unix platforms where flock is not supported, even though it may
exist in the libc crate.

std/src/fs/tests.rs

@@ -204,6 +204,13 @@ fn file_test_io_seek_and_write() {
 }
 
 #[test]
+#[cfg(any(
+    windows,
+    target_os = "freebsd",
+    target_os = "linux",
+    target_os = "netbsd",
+    target_vendor = "apple",
+))]
 fn file_lock_multiple_shared() {
     let tmpdir = tmpdir();
     let filename = &tmpdir.join("file_lock_multiple_shared_test.txt");
@@ -220,6 +227,13 @@ fn file_lock_multiple_shared() {
 }
 
 #[test]
+#[cfg(any(
+    windows,
+    target_os = "freebsd",
+    target_os = "linux",
+    target_os = "netbsd",
+    target_vendor = "apple",
+))]
 fn file_lock_blocking() {
     let tmpdir = tmpdir();
     let filename = &tmpdir.join("file_lock_blocking_test.txt");
@@ -237,6 +251,13 @@ fn file_lock_blocking() {
 }
 
 #[test]
+#[cfg(any(
+    windows,
+    target_os = "freebsd",
+    target_os = "linux",
+    target_os = "netbsd",
+    target_vendor = "apple",
+))]
 fn file_lock_drop() {
     let tmpdir = tmpdir();
     let filename = &tmpdir.join("file_lock_dup_test.txt");
@@ -251,6 +272,13 @@ fn file_lock_drop() {
 }
 
 #[test]
+#[cfg(any(
+    windows,
+    target_os = "freebsd",
+    target_os = "linux",
+    target_os = "netbsd",
+    target_vendor = "apple",
+))]
 fn file_lock_dup() {
     let tmpdir = tmpdir();
     let filename = &tmpdir.join("file_lock_dup_test.txt");

std/src/sys/pal/unix/fs.rs

@@ -1254,16 +1254,54 @@ impl File {
         }
     }
 
+    #[cfg(any(
+        target_os = "freebsd",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    ))]
     pub fn lock(&self) -> io::Result<()> {
         cvt(unsafe { libc::flock(self.as_raw_fd(), libc::LOCK_EX) })?;
         return Ok(());
     }
 
+    #[cfg(not(any(
+        target_os = "freebsd",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    )))]
+    pub fn lock(&self) -> io::Result<()> {
+        Err(io::const_io_error!(io::ErrorKind::Unsupported, "lock() not supported"))
+    }
+
+    #[cfg(any(
+        target_os = "freebsd",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    ))]
     pub fn lock_shared(&self) -> io::Result<()> {
         cvt(unsafe { libc::flock(self.as_raw_fd(), libc::LOCK_SH) })?;
         return Ok(());
     }
 
+    #[cfg(not(any(
+        target_os = "freebsd",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    )))]
+    pub fn lock_shared(&self) -> io::Result<()> {
+        Err(io::const_io_error!(io::ErrorKind::Unsupported, "lock_shared() not supported"))
+    }
+
+    #[cfg(any(
+        target_os = "freebsd",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    ))]
     pub fn try_lock(&self) -> io::Result<bool> {
         let result = cvt(unsafe { libc::flock(self.as_raw_fd(), libc::LOCK_EX | libc::LOCK_NB) });
         if let Err(ref err) = result {
@@ -1275,6 +1313,22 @@ impl File {
         return Ok(true);
     }
 
+    #[cfg(not(any(
+        target_os = "freebsd",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    )))]
+    pub fn try_lock(&self) -> io::Result<bool> {
+        Err(io::const_io_error!(io::ErrorKind::Unsupported, "try_lock() not supported"))
+    }
+
+    #[cfg(any(
+        target_os = "freebsd",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    ))]
     pub fn try_lock_shared(&self) -> io::Result<bool> {
         let result = cvt(unsafe { libc::flock(self.as_raw_fd(), libc::LOCK_SH | libc::LOCK_NB) });
         if let Err(ref err) = result {
@@ -1286,11 +1340,37 @@ impl File {
         return Ok(true);
     }
 
+    #[cfg(not(any(
+        target_os = "freebsd",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    )))]
+    pub fn try_lock_shared(&self) -> io::Result<bool> {
+        Err(io::const_io_error!(io::ErrorKind::Unsupported, "try_lock_shared() not supported"))
+    }
+
+    #[cfg(any(
+        target_os = "freebsd",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    ))]
     pub fn unlock(&self) -> io::Result<()> {
         cvt(unsafe { libc::flock(self.as_raw_fd(), libc::LOCK_UN) })?;
         return Ok(());
     }
 
+    #[cfg(not(any(
+        target_os = "freebsd",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    )))]
+    pub fn unlock(&self) -> io::Result<()> {
+        Err(io::const_io_error!(io::ErrorKind::Unsupported, "unlock() not supported"))
+    }
+
     pub fn truncate(&self, size: u64) -> io::Result<()> {
         let size: off64_t =
             size.try_into().map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?;