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/stdlib_test.cpp b/tests/stdlib_test.cpp
index 5b81834..6679480 100644
--- a/tests/stdlib_test.cpp
+++ b/tests/stdlib_test.cpp
@@ -22,6 +22,7 @@
 #include <pthread.h>
 #include <stdint.h>
 #include <stdlib.h>
+#include <sys/cdefs.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ -632,7 +633,7 @@
   AssertChildExited(pid, 99);
 }
 
-#if defined(MUSL)
+#if defined(ANDROID_HOST_MUSL)
 // musl doesn't have getpt
 int getpt() {
   return posix_openpt(O_RDWR|O_NOCTTY);
@@ -968,7 +969,7 @@
 }
 
 TEST(stdlib, getprogname) {
-#if defined(__GLIBC__) || defined(MUSL)
+#if defined(__GLIBC__) || defined(ANDROID_HOST_MUSL)
   GTEST_SKIP() << "glibc and musl don't have getprogname()";
 #else
   // You should always have a name.
@@ -979,7 +980,7 @@
 }
 
 TEST(stdlib, setprogname) {
-#if defined(__GLIBC__) || defined(MUSL)
+#if defined(__GLIBC__) || defined(ANDROID_HOST_MUSL)
   GTEST_SKIP() << "glibc and musl don't have setprogname()";
 #else
   // setprogname() only takes the basename of what you give it.