Prepare to run (select) tests during Emscripten build
...by e.g. executing generated Wasm code with node. This requires check targets
to not be skipped unconditionally, unlike for other CROSS_COMPILING builds, so
introduce gb_CAN_EXECUTE_HOST_CODE to distinguish these cases.
Which revealed that some CppunitTest targets unconditionally used artefacts that
are covered by some ENABLE_WASM_STRIP_*, so made those uses conditional
accordingly (even though the resulting binaries might actually be dysfunctional,
lacking relevant parts; we'll fix that if and when we actually build and run
them).
Change-Id: I7144eeb908ede25358a3c8186198ac532de4d9f1
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/166931
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>