Update libc dependency to 0.2.57

There were some breaking changes between 0.2.55 and 0.2.57.  Now Nix
will only work with the later version.

1 files changed, 1 insertions, 1 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 16837142..2f734aec 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,7 +16,7 @@ exclude     = [
 ]
 
 [dependencies]
-libc = "0.2.55"
+libc = "0.2.57"
 bitflags = "1.0"
 cfg-if = "0.1.0"
 void = "1.0.2"