bear fails to cross build from source for three quite distinct issues:

1. bear is built as an ExternalProject from cmake. Unfortunately, the
   ExternalProject does not pass down all relevant build tools. In
   particular, the C compiler and pkg-config go missing. As a result,
   cmake detects the wrong tools and fails.

2. bear uses grpc, which is not Multi-Arch tagged and thus installed for
   the host architetcure. The relevant plugin cannot be run then. Fixing
   this is likely out of scope for bear.

3. bear runs its test suite during dh_auto_build. Therefore the
   automatic support for DEB_BUILD_OPTIONS=nocheck in debhelper does not
   work. During cross builds, test suites must be disabled as they
   cannot be run.

The attached patch fixes the first and last issue. The grpc issue needs
a separate bug report. Please consider applying it and close this bug
when doing so.

Helmut