Windows build fixes.
Windows build fixes.

Quote uses of $HAS_BK so that spaces and parens in the
path don't break things (ie /c/Program Files (x86)/BitKeeper)

bk: 572cb011glOEL3Cx0KXnlDkUB9Zs-g
bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper