Why not fail if /usr/bin/file fails?

Hi. I'm trying to build https://aur.archlinux.org/packages/mingw-w64-libunistring. Libtool thinks that the installed dependency libiconv.dll.a has unknown type and refuses to build libunistring dll. The libtool script calls `file` internally to detect the type, but it suppresses the error

Can't make dll out of a static convenience library: This system cannot link to static lib

Hi. I'm trying to build mingw-w64-gnutls 3.6.12 on Archlinux. At some point it wants to make a C++ dll out of a C convenience static library and a C++ object file, but libtool omits the static library and link fails with undefined reference. I don't understand why libtool omits the static