I cannot use it from the command line.  May someone tell use how to use.

PS C:\> cd 'C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\ClangC2\bin\amd64'
PS C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\ClangC2\bin\amd64> ./clang.exe D:\tmp\test.cpp -o D:\tmp\test.exe
error: failed to load c2 (file not found)
PS C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\ClangC2\bin\amd64> cat D:\tmp\test.cpp
#include <iostream>

int main() {
    std::cout << "Hello, world!" << std::endl;
    return 0;
}
PS C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\ClangC2\bin\amd64> (ls .\amd64).Name
c2.dll