after r114507 cannot build on msys

[Jarek Czekalski]

In r114506 configure say dup2: yes.

In r114507: dup2: no

configure:22632: checking whether dup2 works
configure:22691: gcc -I /c/Temp/src/emacs/nt/inc -std=gnu99 -o 
conftest.exe -g3 -O2 -gdwarf-2 -mtune=pentium4    conftest.c >&5
configure:22691: $? = 0
configure:22691: ./conftest.exe
configure:22691: $? = 2
configure: program exited with status 2
configure: failed program was:

When it tries to build dup2.c it cannot find msvc-inval.h - I don't have 
such file. Previously this was not build, because dup2 was detected ok.

I have libcrtdll from mingw-runtime-3.14.tar. In this file is dup2 function.

Any hints? I know 114507 added new tests to dup2, but I wonder whether 
my dup2 is really invalid or is it a bug in configure?
What are the impressions of other mingw builders?

Jarek