Auto merge of #12728 - upsuper:fix-libc-unused, r=emilio

Remove unused libc dependency for windows in style

<!-- Please describe your changes on the following line: -->

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [x] These changes do not require tests because its a trivial change to remove unused dependency

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/12728)
<!-- Reviewable:end -->

components/style/Cargo.toml

@@ -31,7 +31,6 @@ gecko_bindings = {path = "../../ports/geckolib/gecko_bindings", optional = true}
 heapsize = {version = "0.3.0", optional = true}
 heapsize_plugin = {version = "0.1.2", optional = true}
 lazy_static = "0.2"
-libc = "0.2"
 log = "0.3.5"
 matches = "0.1"
 num-traits = "0.1.32"
@@ -51,5 +50,8 @@ plugins = {path = "../plugins", optional = true}
 [target.'cfg(windows)'.dependencies]
 kernel32-sys = "0.2"
 
+[target.'cfg(not(windows))'.dependencies]
+libc = "0.2"
+
 [build-dependencies]
 walkdir = "0.1"

components/style/lib.rs

@@ -51,7 +51,6 @@ extern crate gecko_bindings;
 #[allow(unused_extern_crates)]
 #[macro_use]
 extern crate lazy_static;
-extern crate libc;
 #[macro_use]
 extern crate log;
 #[allow(unused_extern_crates)]

components/style/workqueue.rs

@@ -11,10 +11,10 @@
 
 #[cfg(windows)]
 extern crate kernel32;
+#[cfg(not(windows))]
+extern crate libc;
 
 use deque::{self, Abort, Data, Empty, Stealer, Worker};
-#[cfg(not(windows))]
-use libc::usleep;
 use rand::{Rng, XorShiftRng, weak_rng};
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::mpsc::{Receiver, Sender, channel};
@@ -90,7 +90,7 @@ const BACKOFFS_UNTIL_CONTROL_CHECK: u32 = 6;
 #[cfg(not(windows))]
 fn sleep_microseconds(usec: u32) {
     unsafe {
-        usleep(usec);
+        libc::usleep(usec);
     }
 }