Redefine functions with test hooks only for tests

Android build has issues with these defines, this will allow the build to
succeed if it doesn't need to build the tests.

test/unit/test_hooks.c

@@ -12,7 +12,7 @@ func_to_hook(int arg1, int arg2) {
 	return arg1 + arg2;
 }
 
-#define func_to_hook JEMALLOC_HOOK(func_to_hook, test_hooks_libc_hook)
+#define func_to_hook JEMALLOC_TEST_HOOK(func_to_hook, test_hooks_libc_hook)
 
 TEST_BEGIN(unhooked_call) {
 	test_hooks_libc_hook = NULL;