Fix $(PWD) issue for Windows makefile
Fix $(PWD) issue for Windows makefile

Seems $(PWD) if the shell is powershell may not be inherited properly
as it ends up being an empty string. The result of this is that using
mingw's make with powershell is that $(PWD)/bin ends up being /bin and the
windows shim will get placed there. make install afterwards will try to find
the shim at $pwd/bin and fail.

Changing to CURDIR https://www.gnu.org/software/make/manual/make.html#index-CURDIR
seems to be a solution here as it's not inherited by the environment and
is set by make itself so should work across any type of shell.

Signed-off-by: Daniel Canter <8d0fd95ae71f7e4870b010b10f83a6201b034a65@microsoft.com>

dmcgowan/containerd,estesp/containerd,estesp/containerd,dmcgowan/containerd,containerd/containerd,mikebrow/containerd,containerd/containerd,thaJeztah/containerd,thaJeztah/containerd,mikebrow/containerd