Fix RUN_IN_BUILD_ENV for Win32 builds with pmcpp.
Fix RUN_IN_BUILD_ENV for Win32 builds with pmcpp.

The ways of Windows path resolution are subtle and bizarre
in the extreme.  Using "../" (dot,dot,forward-slash) is not
allowed apparently (backslashes are OK with relative paths)
and the DOS shell (cmd.exe) produces this error:

"'..' is not recognized as an internal or external command,
operable program or batch file."

We can workaround this by using a path from the drive root,
even though it still contains "../" components.

tjanez/pcp,tjanez/pcp,aeg-aeg/pcpfans,andyvand/cygpcpfans,wuliming/pcp,adfernandes/pcp,mbaldessari/pcp,mbaldessari/pcp,aeg-aeg/pcpfans,wuliming/pcp,edwardt/pcp,andyvand/cygpcpfans,andyvand/cygpcpfans,edwardt/pcp,andyvand/cygpcpfans,edwardt/pcp,andyvand/cygpcpfans,ryandoyle/pcp_original,edwardt/pcp,mbaldessari/pcp,prasincs/pcp,tjanez/pcp,aeg-aeg/pcpfans,tjanez/pcp,ryandoyle/pcp_original,wuliming/pcp,andyvand/cygpcpfans,edwardt/pcp,tjanez/pcp,aeg-aeg/pcpfans,tjanez/pcp,adfernandes/pcp,prasincs/pcp,aeg-aeg/pcpfans,mbaldessari/pcp,prasincs/pcp,tjanez/pcp,wuliming/pcp,ryandoyle/pcp_original,andyvand/cygpcpfans,prasincs/pcp,edwardt/pcp,aeg-aeg/pcpfans,adfernandes/pcp,ryandoyle/pcp_original,adfernandes/pcp,prasincs/pcp,mbaldessari/pcp,mbaldessari/pcp,ryandoyle/pcp_original,edwardt/pcp,prasincs/pcp,prasincs/pcp,adfernandes/pcp,wuliming/pcp,tjanez/pcp,adfernandes/pcp,ryandoyle/pcp_original,wuliming/pcp,ryandoyle/pcp_original,edwardt/pcp,wuliming/pcp,aeg-aeg/pcpfans,aeg-aeg/pcpfans,adfernandes/pcp,wuliming/pcp,andyvand/cygpcpfans,adfernandes/pcp,prasincs/pcp,ryandoyle/pcp_original