CMake: Use CMAKE_C_COMPILER_ARG1 when building dependencies.

CMAKE_C_COMPILER_ARG1 is set in CMake toolchain file
cmake/i386-linux-gnu.toolchain.cmake. Use when compiling dependencies to
simplify 32-bit builds.
Merge #1033 'Automatic dependency rebuilding: Pass CMAKE_C_COMPILER_ARG1 to deps building.'
Update busted to 2.0.rc3.

Default to verbose output to show more information in case of errors.
Fix #1031.