...for now; workdir/UnpackedTarball/icu/source/tools/toolutil/Makefile invokes
the compiler with a -DU_HOST=\"...\" argument, and apparently directly executes
the compiler from CreateProcess, not going via a shell invocation for the recipe
line.  This confuses clang-cl for whatever reason, and for whatever other
reason, forcing make to go via a shell invocation (by adding "true &&" into the
recipe line) fixes it.

Change-Id: I3757a8856f93228c19475b37f3037fa9519a426f