Add instructions on how to use CMake to compile libxml

INSTALL.libxml2

@@ -27,6 +27,26 @@ Compilation
 
      Please report test failures to the mailing list or bug tracker.
 
+     Another option for compiling libxml is using CMake:
+
+         cmake -E tar xf libxml2-xxx.tar.gz
+         cmake -S libxml2-xxx -B libxml2-xxx-build [possible options]
+         cmake --build libxml2-xxx-build
+         cmake --install libxml2-xxx-build
+
+     Common CMake options include:
+
+         -D BUILD_SHARED_LIBS=OFF            # build static libraries
+         -D CMAKE_BUILD_TYPE=Release         # specify build type
+         -D CMAKE_INSTALL_PREFIX=/usr/local  # specify the install path
+         -D LIBXML2_WITH_ICONV=OFF           # disable iconv
+         -D LIBXML2_WITH_LZMA=OFF            # disable liblzma
+         -D LIBXML2_WITH_PYTHON=OFF          # disable Python
+         -D LIBXML2_WITH_ZLIB=OFF            # disable libz
+
+     You can also open the libxml source directory with its CMakeLists.txt
+     directly in various IDEs such as CLion, QtCreator, or Visual Studio.
+
   2. What other libraries are needed to compile/install libxml?
 
      Libxml does not require any other libraries. A platform with somewhat