BoostTestTargets.cmake requires the CMake-configurable form of the Boost
test framework to be used (i.e. "#include <BoostTestTargetConfig.h>"), and
checks each test source code file for this, outputting a warning in case
this requirement is not met.
Unfortunately, a conditional in the check is badly specified (the CMake
variable syntax is not followed), so the warning is emitted even when it
should not be.
This patch fixes this bug and restores the correct behavior.
Submitted upstream at https://github.com/rpavlik/cmake-modules/pull/44
