[clang][deps] Move SingleCommandCompilationDatabase to a header

This makes `SingleCommandCompilationDatabase` reusable.

Author: jansvoboda11

clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h

@@ -30,6 +30,24 @@ namespace dependencies {
 
 class DependencyScanningWorkerFilesystem;
 
+/// Compilation database that holds and reports a single compile command.
+class SingleCommandCompilationDatabase : public CompilationDatabase {
+  CompileCommand Command;
+
+public:
+  SingleCommandCompilationDatabase(CompileCommand Cmd)
+      : Command(std::move(Cmd)) {}
+
+  std::vector<CompileCommand>
+  getCompileCommands(StringRef FilePath) const override {
+    return {Command};
+  }
+
+  std::vector<CompileCommand> getAllCompileCommands() const override {
+    return {Command};
+  }
+};
+
 class DependencyConsumer {
 public:
   virtual ~DependencyConsumer() {}

clang/tools/clang-scan-deps/ClangScanDeps.cpp

@@ -201,24 +201,6 @@ llvm::cl::opt<bool> Verbose("v", llvm::cl::Optional,
 
 } // end anonymous namespace
 
-class SingleCommandCompilationDatabase : public tooling::CompilationDatabase {
-public:
-  SingleCommandCompilationDatabase(tooling::CompileCommand Cmd)
-      : Command(std::move(Cmd)) {}
-
-  std::vector<tooling::CompileCommand>
-  getCompileCommands(StringRef FilePath) const override {
-    return {Command};
-  }
-
-  std::vector<tooling::CompileCommand> getAllCompileCommands() const override {
-    return {Command};
-  }
-
-private:
-  tooling::CompileCommand Command;
-};
-
 /// Takes the result of a dependency scan and prints error / dependency files
 /// based on the result.
 ///