Update README.md.

README.md

@@ -318,20 +318,33 @@ cmake -B build -S .
 cmake --build build
 ```
 
+Force 64-bit build:
+```
+cmake -D64BIT=1 -B build -S .
+cmake --build build
+```
+
 ### Building with waf
 
 To use waf, you need to install python (2.7 minimum)
 
 ```
-(./waf configure -T release)
-(./waf)
+./waf configure -T release
+./waf
+```
+
+Force 64-bit build:
+```
+./waf configure -T release -8
+./waf
 ```
 
 ## Build options
 
 Some useful build options that can be set during the cmake step.
 
-* **GOLDSOURCE_SUPPORT** - allows to turn off/on the support for GoldSource input. Set to **ON** by default on Windows and Linux, **OFF** on other platforms.
+* **GOLDSOURCE_SUPPORT** - allows to turn off/on the support for GoldSource input. Set to **ON** by default on Windows, Linux and MacOS, **OFF** on other platforms.
+* **64BIT** - allows to turn off/on 64-bit build. Set to **OFF** by default on x86_64 Windows, x86_64 Linux and 32-bit platforms, **ON** on other 64-bit platforms.
 * **USE_VGUI** - whether to use VGUI library. **OFF** by default. You need to init `vgui_support` submodule in order to build with VGUI.
 
 This list is incomplete. Look at `CMakeLists.txt` to see all available options.