Avoid 'expr index' on Mac OS X as it isn't supported
Avoid 'expr index' on Mac OS X as it isn't supported

This fixes git-instaweb so it can start an httpd without warning
about an invalid test command.  Yes its ugly, but its also quite
portable.

Signed-off-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git