linux: fix a warning in the process_util unittest

base/process_util_unittest.cc

Index: base/process_util_unittest.cc
diff --git a/base/process_util_unittest.cc b/base/process_util_unittest.cc
index 4169dc6b1ec26a5dc9cfcf95aff8744adfd8a62e..e60f923c52d3e3259ba0115df50c2293f782373c 100644
--- a/base/process_util_unittest.cc
+++ b/base/process_util_unittest.cc
@@ -415,7 +415,11 @@ TEST_F(OutOfMemoryTest, Memalign) {
 }
 
 TEST_F(OutOfMemoryTest, Posix_memalign) {
-  ASSERT_DEATH(posix_memalign(&value_, 8, test_size_), "");
+  // Grab the return value of posix_memalign to silence a compiler
+  // warning about unused variables.  We don't actually care about
+  // the return value, since we're asserting death.
+  int ret;
+  ASSERT_DEATH(ret = posix_memalign(&value_, 8, test_size_), "");
 }
 
 extern "C" {