Android; Add additional check before using membarrier (#8320)

Calling membarrier on Android before version Q can kill the whole process. 
This implements an additional check when build with TARGET_ANDROID.
Refactor the check in a separate function as it got quite large.

src/Native/gc/unix/gcenv.unix.cpp

@@ -168,6 +168,39 @@ enum membarrier_cmd
     MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE  = (1 << 6)
 };
 
+bool CanFlushUsingMembarrier()
+{
+#ifdef TARGET_ANDROID
+    // Calling membarrier on older Android versions can just kill the process
+#ifdef __ANDROID_API_Q__    
+    int api_level = android_get_device_api_level();
+
+    if (api_level < __ANDROID_API_Q__)
+    {
+        return false;
+    }
+#else
+    return false;
+#endif // __ANDROID_API_Q__
+
+#endif // TARGET_ANDROID
+
+    // Starting with Linux kernel 4.14, process memory barriers can be generated
+    // using MEMBARRIER_CMD_PRIVATE_EXPEDITED.
+
+    int mask = membarrier(MEMBARRIER_CMD_QUERY, 0);
+
+    if (mask >= 0 &&
+        mask & MEMBARRIER_CMD_PRIVATE_EXPEDITED &&
+        // Register intent to use the private expedited command.
+        membarrier(MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED, 0) == 0)
+    {
+        return true;
+    }
+
+    return false;
+}
+
 //
 // Tracks if the OS supports FlushProcessWriteBuffers using membarrier
 //
@@ -324,17 +357,9 @@ bool GCToOSInterface::Initialize()
 
     assert(s_flushUsingMemBarrier == 0);
 
-    // Starting with Linux kernel 4.14, process memory barriers can be generated
-    // using MEMBARRIER_CMD_PRIVATE_EXPEDITED.
-    int mask = membarrier(MEMBARRIER_CMD_QUERY, 0);
-    if (mask >= 0 &&
-        mask & MEMBARRIER_CMD_PRIVATE_EXPEDITED &&
-        // Register intent to use the private expedited command.
-        membarrier(MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED, 0) == 0)
-    {
-        s_flushUsingMemBarrier = TRUE;
-    }
-    else
+    s_flushUsingMemBarrier = CanFlushUsingMembarrier();
+
+    if (!s_flushUsingMemBarrier)
     {
         assert(g_helperPage == 0);