Details
P2: Important Description
includeOption(const HeaderPath &p) should return -isystem instead of -I for system header path otherwise build is broken.
Look at the difference:
$ clang++ -E -x c++ - -v < /dev/null #include <...> search starts here: /usr/include/c++/v1 /usr/bin/../lib/clang/4.0.0/include /usr/include End of search list. $ clang++ -nostdinc -isystem /usr/include/c++/v1 -isystem /usr/bin/../lib/clang/4.0.0/include -isystem /usr/include -E -x c++ - -v < /dev/null #include <...> search starts here: /usr/include/c++/v1 /usr/bin/../lib/clang/4.0.0/include /usr/include End of search list. $ clang++ -nostdinc -I/usr/include/c++/v1 -I/usr/bin/../lib/clang/4.0.0/include -I/usr/include -E -x c++ - -v < /dev/null #include <...> search starts here: /usr/bin/../lib/clang/4.0.0/include /usr/include /usr/include/c++/v1 End of search list.