This is to catch an error where tests are run without first
building what are being tested. Relying on prefixing $PATH with
the build directory and expect that the PATH mechanism would
find what we just built would silently run an already installed
binaries from the PATH.
Signed-off-by: Alex Riesen <raa.lkml@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>