So I tried with msys instead from the nt subdirectory. "make bootstrap"
goes much further, but it now ends with
Directory textmodes
Directory url
Directory obsolete
Generating cus-load.el...
Saving file c:/eclean/bld/emacs/lisp/cus-load.el...
Loading vc-cvs...
Wrote c:/eclean/bld/emacs/lisp/cus-load.el
Generating cus-load.el...done
rm "./../bin/emacs.exe"
make[1]: Leaving directory `/c/eclean/bld/emacs/lisp'
make - --unix -C ../lib-src DOC
[Please ignore a syntax error on the next line - it is intentional]
/bin/sh.exe: -c: line 1: unexpected EOF while looking for matching `"'
/bin/sh.exe: -c: line 2: syntax error: unexpected end of file
make[1]: Entering directory `/c/eclean/bld/emacs/lib-src'
mkdir "oo-spd"
mkdir "oo-spd/i386"
echo oo-spd/i386 > stamp_BLD
gcc -I. -DWIN32_LEAN_AND_MEAN -D_WIN32_WINNT=0x0400 -D_X86_=1 -c
-gstabs+ -g3 -
mtune=pentium4 -O2 -Di386 -D_CRTAPI1=_cdecl -Ic:/g/include
-DWINDOWSNT -DDOS_N
T -DSTDC_HEADERS=1 -DNO_LDAV=1 -DNO_ARCHIVES=1 -DHAVE_CONFIG_H=1
-I../nt/inc -I.
./src -o oo-spd/i386/make-docfile.o make-docfile.c
gcc -I. -DWIN32_LEAN_AND_MEAN -D_WIN32_WINNT=0x0400 -D_X86_=1 -c
-gstabs+ -g3 -
mtune=pentium4 -O2 -Di386 -D_CRTAPI1=_cdecl -Ic:/g/include
-DWINDOWSNT -DDOS_N
T -DSTDC_HEADERS=1 -DNO_LDAV=1 -DNO_ARCHIVES=1 -DHAVE_CONFIG_H=1
-I../nt/inc -I.
./src -o oo-spd/i386/ntlib.o ntlib.c
gcc -o oo-spd/i386/make-docfile.exe -gstabs+ -g3
oo-spd/i386/make-docfile.o o
o-spd/i386/ntlib.o -ladvapi32
make[1]: *** No rule to make target
`../lisp/international/charprop.el', needed
by `DOC'. Stop.
make[1]: Leaving directory `/c/eclean/bld/emacs/lib-src'
make: *** [bootstrap-gmake] Error 2