Ignore the style executable used for testing

Susurrus · Susurrus · commit 0881a59eccaa · 2019-01-23T09:00:09.000-08:00
This is used for running style checks on the libc codebase but shouldn't
be committed, so adding it to the .gitignore file.
diff --git a/.gitignore b/.gitignore
@@ -1,3 +1,4 @@
 target
 Cargo.lock
 *~
+style

-Original file line number
+Diff line change
@@ @@ -1,3 +1,4 @@ @@
 target
 Cargo.lock
 *~
 +style