Quick build fix

Added missing function declaration.

Change-Id: I52ddb666d70733187242906d298fb986f413756a
Reviewed-on: https://swiftshader-review.googlesource.com/19208
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>
diff --git a/src/OpenGL/common/Image.hpp b/src/OpenGL/common/Image.hpp
index 4fed893..d7117c5 100644
--- a/src/OpenGL/common/Image.hpp
+++ b/src/OpenGL/common/Image.hpp
@@ -79,6 +79,7 @@
 	void release();
 	void* lock(int x, int y, int z);
 	void unlock();
+	bool targetRequiresSync() const;
 
 private:
 	int width;