Create a CMake macro to handle project specific options

[white238]

cmake_dependent_option just doesn't work like I always think it should so we should create our own called serac_project_specific_option that encapsulates the behavior we want.

For example:

• ENABLE_BENCHMARKS is a global BLT created option, it is used for multiple projects. Allow a user to turn that on and honor it
• Unless the project specific one is set SERAC_ENABLE_BENCHMARKS then honor that one.
• Always create a SERAC_ENABLE_BENCHMARKS because the rest of our build system is guarded on that

[chapman39]

personally i like the way cmake_dependent_option works. pretty much, you can't set the project-specific option without ensuring the general one is true. so if you want to enable benchmarks, we should just set ENABLE_BENCHMARKS. it will automatically enable SERAC_ENABLE_BENCHMARKS.

let me know your thoughts @white238 @samuelpmish

[chapman39]

from a discussion with @tupek2 : it would be nice to somehow set -DSMITH_ENABLE_BENCHMARKS=ON and only set that project's benchmarks... im not sure if that would work though, since we need to also set -DENABLE_BENCHMARKS=ON for BLT to setup benchmarking properly.

another thing to consider is these options need to be set properly before BLT is called, which would mean moving this call https://github.com/LLNL/serac/blob/develop/CMakeLists.txt#L127 which may complicate things in the case BLT changes/ adds options, we need to match BLT.

include(${BLT_SOURCE_DIR}/SetupBLT.cmake)

#------------------------------------------------------------------------------
# Setup Macros/Basics
#------------------------------------------------------------------------------

include(${PROJECT_SOURCE_DIR}/cmake/SeracMacros.cmake)
include(${PROJECT_SOURCE_DIR}/cmake/SeracBasics.cmake) # this would need to be called before setupBLT
include(${PROJECT_SOURCE_DIR}/cmake/SeracCompilerFlags.cmake)