Replace local MUSL define with global ANDROID_HOST_MUSL

Bug: 190084016
Test: m USE_HOST_MUSL=true bionic-unit-tests-glibc
Change-Id: I56b23576cb24912112d2ae56d8ecc2e3716982fe
diff --git a/tests/malloc_test.cpp b/tests/malloc_test.cpp
index f15fc75..eae44ce 100644
--- a/tests/malloc_test.cpp
+++ b/tests/malloc_test.cpp
@@ -27,6 +27,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/auxv.h>
+#include <sys/cdefs.h>
 #include <sys/prctl.h>
 #include <sys/types.h>
 #include <sys/wait.h>
@@ -59,7 +60,7 @@
 
 #define HAVE_REALLOCARRAY __GLIBC_PREREQ(2, 26)
 
-#elif defined(MUSL)
+#elif defined(ANDROID_HOST_MUSL)
 
 #define HAVE_REALLOCARRAY 1
 
@@ -659,7 +660,7 @@
 }
 
 TEST(malloc, mallopt_smoke) {
-#if !defined(MUSL)
+#if !defined(ANDROID_HOST_MUSL)
   errno = 0;
   ASSERT_EQ(0, mallopt(-1000, 1));
   // mallopt doesn't set errno.