Feature #2670

Updated by Junxiao Shi over 6 years ago

During `./waf configure`, allow selecting a subset of tools. 

 For every tool, `wscript` should automatically define `--enable-X` option and `--disable-X` option, where X is the directory name for the tool.   
 The semantics of those options is: 

 * If any `--enable-`* option is used, only those tools specified by `--enable-`* options are selected. 
 * If no `--enable-`* option is used, all tools excepted those specified by `--disable-`* options are selected. 
 * It's an error to specify both `--enable-X` and `--disable-X` for tool X. 

 Dependency detection for deselected tools should be skipped.   
 Unit testing for deselected tools should not be built.