Move SyncHelper to platform

... upcoming changes will add promote the emulated virtio gpu
stack as a proper platform backend which will include the
SyncHelper.

Reviewed-by: Aaron Ruby <aruby@blackberry.com>
Acked-by: Yonggang Luo <luoyonggang@gmail.com>
Acked-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27246>

src/gfxstream/guest/platform/include/Sync.h

@@ -0,0 +1,36 @@
+// Copyright 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either expresso or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <cstdint>
+#include <stddef.h>
+
+namespace gfxstream {
+
+// Abstraction around libsync for testing.
+class SyncHelper {
+   public:
+    virtual ~SyncHelper() {}
+
+    virtual int wait(int syncFd, int timeoutMilliseconds) = 0;
+
+    virtual int dup(int syncFd) = 0;
+
+    virtual int close(int syncFd) = 0;
+};
+
+SyncHelper* createPlatformSyncHelper();
+
+}  // namespace gfxstream

src/gfxstream/guest/platform/linux/LinuxSync.cpp

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "LinuxSync.h"
+
+#if defined(__ANDROID__)
+#include <sync/sync.h>
+#endif
+#include <unistd.h>
+
+namespace gfxstream {
+
+LinuxSyncHelper::LinuxSyncHelper() {}
+
+int LinuxSyncHelper::wait(int syncFd, int timeoutMilliseconds) {
+#if defined(__ANDROID__)
+    return sync_wait(syncFd, timeoutMilliseconds);
+#else
+    (void)syncFd;
+    (void)timeoutMilliseconds;
+    return -1;
+#endif
+}
+
+int LinuxSyncHelper::dup(int syncFd) {
+    return ::dup(syncFd);
+}
+
+int LinuxSyncHelper::close(int syncFd) {
+    return ::close(syncFd);
+}
+
+SyncHelper* createPlatformSyncHelper() {
+    return new LinuxSyncHelper();
+}
+
+}  // namespace gfxstream

src/gfxstream/guest/platform/linux/LinuxSync.h

@@ -0,0 +1,32 @@
+// Copyright 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either expresso or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include "Sync.h"
+
+namespace gfxstream {
+
+class LinuxSyncHelper : public SyncHelper {
+   public:
+    LinuxSyncHelper();
+
+    int wait(int syncFd, int timeoutMilliseconds) override;
+
+    int dup(int syncFd) override;
+
+    int close(int syncFd) override;
+};
+
+}  // namespace gfxstream