Makefile Variables

 ==================

 Some Makefile variables are reserved by the GNU Coding Standards for

 the use of the "user" - the person building the package. For instance,

 CXX and CXXFLAGS are such variables, and have the same meaning as

 explained in the previous section. These variables can be set on the

 command line when invoking `make' like this:

 `make [VARIABLE=VALUE]...'

 WARNINGCXXFLAGS is a non-standard Makefile variable introduced by us

 to hold several compiler flags related to warnings. Its default value

 can be overridden when invoking `make'. For example to disable all

 warning flags use `make WARNINGCXXFLAGS='.

 In order to turn off a single flag from the default set of warning

 flags, you can use the CXXFLAGS variable, since this is passed after

 WARNINGCXXFLAGS. For example to turn off `-Wold-style-cast' (which is

 used by default when g++ is detected) you can use

 `make CXXFLAGS="-g -O2 -Wno-old-style-cast"'.