ci: disable ccache when running CMake build system tests
ci: disable ccache when running CMake build system tests

Some tests check if certain files are rebuilt when source files are
'touch'ed. With ccache, 'touch'ing source files doesn't cause a
rebuild, hence the test fails. In case IDF_CCACHE_ENABLE was set in
the environment, unset it before starting the tests.

espressif/esp-idf,espressif/esp-idf,espressif/esp-idf,espressif/esp-idf