Update the compiler-builtins submodule

alexcrichton · alexcrichton · commit 12596893f900 · 2018-07-25T18:12:39.000-07:00
Pull in a fix for rust-lang/libm#129
diff --git a/src/libcompiler_builtins b/src/libcompiler_builtins
@@ -1 +1 @@
-Subproject commit b4a3645cfe102a100b6ebecbe76df37bc957eda8
+Subproject commit 52a6a4d7087d14a35d44a11c39c77fa79d71378d
