win32/Makefile: put mini config.h in correct place in dep tree

win32/Makefile: put mini config.h in correct place in dep tree

I fixed this for GNUMakefile and makefile.mk when I added the parallel
building feature to those 2 but I left nmake unfixed. Now fix it. This
commit allow a "nmake CCTYPE=MSVC90 av.obj" or
"nmake CCTYPE=MSVC90 mini/av.obj" or other individual build product
targets to work on a cleaned src tree, while previously you'd get with
the above commands
        cl -c -nologo -GF -W3 -I..\lib\CORE -I.\include -I. -I.. -DWIN32
-D_CONSOLE -DNO_STRICT -D_CRT_SECURE_NO_DEPRECATE
-D_CRT_NONSTDC_NO_DEPRECATE -DPERLDLL -DPERL_CORE   -O1 -MD -Zi -DNDEBUG
-GL -DPERL_EXTERNAL_GLOB -DPERL_IS_MINIPERL -Fo.\mini\av.obj ..\av.c
av.c
c:\p525\src\perl.h(28) : fatal error C1083: Cannot open include file:
'config.h': No such file or directory
NMAKE : fatal error U1077: '"C:\Program Files\Microsoft Visual Studio 12.0
\VC\BIN\cl.EXE"' : return code '0x2'

Basically, "all" was the only target that worked on a clean src tree with
the nmake makefile previously. Also collapse the catting recipies into
single lines to speed up the mini config.h generation through less proc
starts of cmd.exe by nmake.exe. This reduces the mini config.h target time,
see timings in ticket associated with this comit. Also sync the sentinal
command (.exists) between all 3 mkfs for less diff-ness between the 3
mkfs (debugging aid).