* Clean up quoting and other minor issues
* Reorganize CMake build output
Make it clearer which parts of the output pertain to external projects.
* Use a consistent ordering of ExternalProject arguments
* Prevent the top-level build from running in parallel
This prevents spurious failures when running make -j.
* Actually parse arguments in the xcodebuild function
* Use ExternalProject features when available
* submodule limits from CMake 3.0
* shallow clones from CMake 3.6
* git progress output from CMake 3.8
* Only build the parts of leveldb we need
Skip building the tools and other libraries
* Avoid installing ExternalProjects
Consume build output directly so that we can build just the targets we
need. Installing causes all targets to be built.
This doesn't matter as much for these targets but the gRPC build
includes a ton of stuff we don't need so it's worth adopting this as a
general strategy.
* Define an external build for grpc
* Test that grpc can link successfully.
* Add a FindGRPC CMake module
* Actually comment ExternalProjext_GitSource
