[!740] [latex][bugfix][win32][cmake] ignore CMAKE_FIND_ROOT_PATH for latexmkrc.cmake

Merge branch 'fix-cmake-latexmk' into 'master'

ref:core/dune-common When cross compiling for windows it is necessary to tweak
CMAKE_FIND_ROOT_PATH_MODE_* to modify default behavior of FIND_XXX() commands
to search for headers/libs in the target environment and search for programs
in the build host environment.

This lead to a problem when searching for latexmkrc.cmake.

We now explicitly change the UseLatexMk find_file call to ignore the
CMAKE_FIND_ROOT_PATH and thus beeing able to find the file in the source
directory.

@gruenich can we backport this to 2.7?

See merge request [!740]

  [!740]: gitlab.dune-project.org/core/dune-common/merge_requests/740

cmake/modules/UseLatexMk.cmake

@@ -114,6 +114,7 @@ find_file(LATEXMKRC_TEMPLATE
                 ${CMAKE_SOURCE_DIR}
                 ${CMAKE_SOURCE_DIR}/cmake
                 ${CMAKE_SOURCE_DIR}/cmake/modules
+          NO_CMAKE_FIND_ROOT_PATH
           )
 
 # Add the clean_latex target