Specify path to system libraries for cross-compile

[Artalus]

• Search for <string> in /arm/target/usr/include instead of /usr/include
• Prevent clang builtin limits.h #include_nexting /usr/include/limits.h
• Ensure right primitives' sizeof when targeting different bitness (leading to sizeof(long) != SIZE_OF_LONG)

Clue from #llvm

@filcab [07.05.2018 1:15 PM]
You’ll want to explicitly add the target to your libclang command lines. You might want to add -isysroot too. If all else fails, do what I did for ycm and explicitly add the include paths that your compiler searches (check out the output of a compile with -v)

Can be partially worked around by providing -nostdinc++ -isystem /path/to/usr/include -isystem /path/to/cross-gcc/stdlib in compile_commads.json.

Probably those can be added with a commandline adjuster like the one in clang's CommonOptionsParser.cpp.

Another clue.

Once fixed, apply the same to leak-marker.