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/string_posix_strerror_r_test.cpp b/tests/string_posix_strerror_r_test.cpp
index f3d73d4..e4becaa 100644
--- a/tests/string_posix_strerror_r_test.cpp
+++ b/tests/string_posix_strerror_r_test.cpp
@@ -27,7 +27,7 @@
 
   // Valid.
   ASSERT_EQ(0, posix_strerror_r(0, buf, sizeof(buf)));
-#if defined(MUSL)
+#if defined(ANDROID_HOST_MUSL)
   ASSERT_STREQ("No error information", buf);
 #else
   ASSERT_STREQ("Success", buf);
@@ -35,7 +35,7 @@
   ASSERT_EQ(0, posix_strerror_r(1, buf, sizeof(buf)));
   ASSERT_STREQ("Operation not permitted", buf);
 
-#if defined(__BIONIC__) || defined(MUSL)
+#if defined(__BIONIC__) || defined(ANDROID_HOST_MUSL)
   // Invalid.
   ASSERT_EQ(0, posix_strerror_r(-1, buf, sizeof(buf)));
 # if defined(__BIONIC__)