Commit r21871 fixed the sanity check associated with macro
"SlicerMacroConfigureGenericCxxModuleTests" by testing the content of
the variable.

This approach works well for function. In case of macro, only parameter
referenced using ${argX} are replaced. It means the following code
doesn't work:

// ----------
macro(foo bar)
  set(var "foo")
  message("${var}:${${var}}")
endmacro()

foo("hello")
// ----------

It outputs:

  foo:

whereas the following is expected:

  foo:hello

This commit fix the problem by explicitly testing the parameter value.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21873 3bd1e089-480b-0410-8dfb-8563597acbee