Update README with CMake build instructions

README.md

@@ -30,6 +30,10 @@ QZeroConf can be built directly into your project if your project is [LGPL3](htt
 1. Clone or download QZeroConf.  If you download, unzip.
 2. Enter the qtzeroconf directory, run qmake and then make.
 
+#### Building with CMake
+Use `BUILD_SHARED_LIBS` to control whether QZeroConf should be built as static (`-DBUILD_SHARED_LIBS=OFF`) or as shared (`-DBUILD_SHARED_LIBS=ON`) library.
+The default is `OFF`.
+
 ### API
 
 #### Service Publishing