[CMake] Introduce a check, whether the user runs into FS1532

With a compiler name given to CMAKE_CXX_COMPILER (instead of a path),
the name is correctly expanded on the first run of cmake, but as soon
as the buil didrectory is existent, it is for obscure reasons expanded
into ${CMAKE_BINARY_DIR}/.... To avoid having users run into this bug,
the expanded compiler variable is matched with the build directory prefix.
In that case, an error is issued.

cmake/modules/DuneMacros.cmake

@@ -530,6 +530,13 @@ endmacro(dune_process_dependency_macros)
 # depedencies.
 # Don't forget to call finalize_dune_project afterwards.
 macro(dune_project)
+  # check whether a compiler name instead of compiler path is given, this causes serious problems with older cmake versions.
+  # Unfortunately those errors only surface on a second run, when the build directory already exists. The compiler
+  # variable is then (for obscure reasons) expanded to ${CMAKE_BINARY_DIR}/...
+  if((${CMAKE_CXX_COMPILER} MATCHES "${CMAKE_BINARY_DIR}.*") AND (${CMAKE_VERSION} VERSION_LESS "3.0"))
+    message(FATAL_ERROR "You need to specify an absolute path to your compiler instead of just the compiler name. cmake >= 3.0 fixes this issue.")
+  endif()
+
   # extract information from dune.module
   dune_module_information(${CMAKE_SOURCE_DIR})
   set(ProjectName            "${DUNE_MOD_NAME}")