Update README with --release / --debug examples

Author: rupsis

README.md

@@ -129,19 +129,29 @@ GitHub pages serves up https://raytracing.github.io/.
 
 Building and Running
 ---------------------
-Copies of the source are provided for you to check your work and compare against. If you wish to build
-the provided source, this project uses CMake. To build, go to the root of the project directory and
-run the following commands to create the debug version of every executable:
+Copies of the source are provided for you to check your work and compare against. If you wish to
+build the provided source, this project uses CMake. To build, go to the root of the project
+directory and run the following commands to create the debug version of every executable:
 
     $ cmake -B build
     $ cmake --build build
 
+You should run `cmake -B build` whenever you change your project `CMakeLists.txt` file (like when
+adding a new source file).
+
 You can specify the target with the `--target <program>` option, where the program may be
 `inOneWeekend`, `theNextWeek`, `theRestOfYourLife`, or any of the demonstration programs. By default
 (with no `--target` option), CMake will build all targets.
 
-On Windows, you can build either `debug` (the default) or `release` (the optimized version). To
-specify this, use the `--config <debug|release>` option.
+    $ cmake --build build --target inOneWeekend
+
+You can build either `debug` (the default) or `release` (the optimized version). To specify this,
+use the `--config <debug|release>` option.
+
+    $ cmake --build build --config release
+
+We recommend building and running the `release` version (especially before the final render) for
+fastest results, unless you need extra debugging information of the (default) debug build.
 
 ### CMake GUI on Windows
 You may choose to use the CMake GUI when building on windows.