This adds a script called build.py as well as a lit substitution
called %build that we can use to invoke it. The idea is that
this allows a lit test to build test inferiors without having
to worry about architecture / platform specific differences,
command line syntax, finding / configurationg a proper toolchain,
and other issues. They can simply write something like:
%build --arch=32 -o %t.exe %p/Inputs/foo.cpp
and it will just work. This paves the way for being able to
run lit tests with multiple configurations, platforms, and
compilers with a single test.
Differential Revision: https://reviews.llvm.org/D54914
llvm-svn: 348058
ba968c0d1d