[clangd][query-driver] Extract target

In some cases system includes extractions is not enough, we also need target specific defines.
The problems appears when clang default target is not the same as toolchain's one (GCC cross-compiler, MinGW on Windows).
After this patch `query-driver` also extracts target and adds `--target=<extracted target>` compile option.

Reviewed By: sammccall

Differential Revision: https://reviews.llvm.org/D92012