[Windows] Fix limit on command line size

This reapplies commit d4020ef7, reverted in ac0edc55 because it
broke build of LLDB. This commit contains appropriate changes for LLDB.
The original commit message is below.

Documentation on CreateProcessW states that maximal size of command line
is 32767 characters including ternimation null character. In the
function llvm::sys::commandLineFitsWithinSystemLimits this limit was set
to 32768. As a result if command line was exactly 32768 characters long,
a response file was not created and CreateProcessW was called with
too long command line.

Differential Revision: https://reviews.llvm.org/D83772