gollvm: fix minor memory leak in unit test

Fix memory leak (missing calls to mpc_clear).

Change-Id: If0e59ef7566de039e2e3e8376ecbcd608509973a
Reviewed-on: https://go-review.googlesource.com/46551
Reviewed-by: Cherry Zhang <cherryyz@google.com>
diff --git a/unittests/BackendCore/BackendCABIOracleTests.cpp b/unittests/BackendCore/BackendCABIOracleTests.cpp
index afc4f4c..28b1dbe 100644
--- a/unittests/BackendCore/BackendCABIOracleTests.cpp
+++ b/unittests/BackendCore/BackendCABIOracleTests.cpp
@@ -484,6 +484,8 @@
   mpc_set_d_d(mpc_val2, 3.0, 4.0, GMP_RNDN);
   Bexpression *ccon1 = be->complex_constant_expression(bc64t, mpc_val1);
   Bexpression *ccon2 = be->complex_constant_expression(bc128t, mpc_val2);
+  mpc_clear(mpc_val1);
+  mpc_clear(mpc_val2);
   Bexpression *fn2 = be->function_code_expression(func, loc);
   std::vector<Bexpression *> args2 = {ccon1, ccon2};
   Bexpression *call2 = be->call_expression(func, fn2, args2, nullptr, h.loc());