cmGlobalGenerator: Cleanup GenerateBuildCommand API

All cmGlobalGenerator::GenerateBuildCommand call sites that need to
produce a string now generate "cmake --build" commands.  The remaining
call sites immediately pass the result to cmSystemTools::RunSingleCommand.
Avoid the intermediate string and argument parsing by directly producing a
vector of strings.  Also drop the ignoreErrors argument because no call
sites remain that use it.

Source/cmGlobalVisualStudio6Generator.h

@@ -52,14 +52,16 @@ public:
    * Try running cmake and building a file. This is used for dynalically
    * loaded commands, not as part of the usual build process.
    */
-  virtual std::string GenerateBuildCommand(const char* makeProgram,
-                                           const char *projectName,
-                                           const char *projectDir,
-                                           const char* additionalOptions,
-                                           const char *targetName,
-                                           const char* config,
-                                           bool ignoreErrors,
-                                           bool fast);
+  virtual void GenerateBuildCommand(
+    std::vector<std::string>& makeCommand,
+    const char* makeProgram,
+    const char* projectName,
+    const char* projectDir,
+    const char* targetName,
+    const char* config,
+    bool fast,
+    std::vector<std::string> const& makeOptions = std::vector<std::string>()
+    );
 
   /**
    * Generate the all required files for building this project/tree. This