This patch implements debuginfod and http client libraries with local caching. A few unit and lit tests are included.
The client libraries are only built if the cmake configuration flag is passed:
cmake [...] -DLLVM_ENABLE_DEBUGINFOD_CLIENT=1
LibCURL is required to build the clients.
The standalone tool llvm-debuginfod-find is also provided; it wraps the debuginfod client library.
The lit tests specific to this tool can be run e.g. with:
LIT_FILTER='.*llvm-debuginfod.* ninja -C build check-llvm'
Thanks in advance for comments and critiques!