Fix clang warnings on unused variable and function.

BUG: 20891269
Change-Id: I191d5e54cd9c4a1e85aaa73fa08eeb9810342782
(cherry picked from commit 65625f39c8cc785f4bb3d8a22bf14e758ae23769)
diff --git a/include/gatekeeper/gatekeeper_utils.h b/include/gatekeeper/gatekeeper_utils.h
index 6439242..8ee032b 100644
--- a/include/gatekeeper/gatekeeper_utils.h
+++ b/include/gatekeeper/gatekeeper_utils.h
@@ -44,7 +44,7 @@
     return N;
 }
 
-static int memcmp_s(const void* p1, const void* p2, size_t length) {
+static inline int memcmp_s(const void* p1, const void* p2, size_t length) {
     const uint8_t* s1 = static_cast<const uint8_t*>(p1);
     const uint8_t* s2 = static_cast<const uint8_t*>(p2);
     uint8_t result = 0;