This allows Ubuntu 16.04 to compile AOO with Clang 1.8 on an x86.

Other architectures probably don't work, as Clang 1.8 is pretty
strict about the low-level C++ ABI hacks in main/bridges, but at
least they should fail early in main/bridges instead of the
previous behaviour, where main/bridges compiles nothing when
"$(COM)" != "GCC" and main/i18npool then fails with a mysterious
"error: cannot get uno environments" message.

Patch by: me