Fix bionic tests for undefined __SIGRTMIN in musl

Musl doesn't export __SIGRTMIN, and it is being removed from the
Android wrappers to avoid accidentally referencing bionic's
reserved signals when compiling against musl.

Bug: 190084016
Test: m USE_HOST_MUSL=true host-native -k
Change-Id: I342666a17abc31bbc57b383b5cc881c2752886f7
diff --git a/tests/setjmp_test.cpp b/tests/setjmp_test.cpp
index c9e9a0c..2f891ec 100644
--- a/tests/setjmp_test.cpp
+++ b/tests/setjmp_test.cpp
@@ -81,8 +81,10 @@
     sigset64_t ss;
     sigemptyset64(&ss);
     sigaddset64(&ss, SIGUSR1 + offset);
+#if defined(__BIONIC__)
     // TIMER_SIGNAL.
     sigaddset64(&ss, __SIGRTMIN);
+#endif
     sigaddset64(&ss, SIGRTMIN + offset);
     return ss;
   }
diff --git a/tests/signal_test.cpp b/tests/signal_test.cpp
index 5bda8b3..7f7f3db 100644
--- a/tests/signal_test.cpp
+++ b/tests/signal_test.cpp
@@ -34,6 +34,13 @@
 
 using namespace std::chrono_literals;
 
+#if defined(ANDROID_HOST_MUSL)
+// Musl doesn't export __SIGRTMIN and __SIGRTMAX, #define
+// them here.
+#define __SIGRTMIN 32
+#define __SIGRTMAX 64
+#endif
+
 static int SIGNAL_MIN() {
   return 1; // Signals start at 1 (SIGHUP), not 0.
 }
diff --git a/tests/string_test.cpp b/tests/string_test.cpp
index 30c87dc..38957e2 100644
--- a/tests/string_test.cpp
+++ b/tests/string_test.cpp
@@ -136,7 +136,7 @@
   // A real-time signal.
   ASSERT_STREQ("Real-time signal 14", strsignal(SIGRTMIN + 14));
   // One of the signals the C library keeps to itself.
-  ASSERT_STREQ("Unknown signal 32", strsignal(__SIGRTMIN));
+  ASSERT_STREQ("Unknown signal 32", strsignal(32));  // __SIGRTMIN
 
   // Errors.
   ASSERT_STREQ("Unknown signal -1", strsignal(-1)); // Too small.