Unhelpful behaviour on Cygwin when "file" isn't installed

[Olly Betts]

I tried to search for previous references to this issue, but it's pretty much
impossible to usefully search for "file"!  Sorry if this is rehashing old
discussions.

A user reported a problem trying to build my libtool-ed project on cygwin.
The problem turned out to be that cygwin apparently doesn't install the
"file" utility by default, but libtool tries to use it without checking
if it is available (in func_win32_libid it seems).  I'm using libtool 1.5.22.
Here's the output in question:

/bin/sh ../libtool --tag=CXX --mode=link g++ -Wall -Wno-unused 
-Wno-uninitialized -I/usr/local/include    -o xapian.la -rpath 
/cygdrive/c/wamp/php/ext -L/cygdrive/c/wamp/php/ -lphp5apache2 -avoid-version 
-module -no-undefined -Wl,--enable-runtime-pseudo-reloc xapian_wrap.lo 
-Wl,--warn-unresolved-symbols -Wl,--enable-runtime-pseudo-reloc 
/usr/local/lib/libxapian.la -lstdc++

*** Warning: linker path does not have real file for library -lphp5apache2.
*** I have the capability to make that library automatically link in when
*** you link to this library.  But I can only do this if you have a
*** shared version of the library, which you do not appear to have
*** because I did check the linker path looking for a file starting
*** with libphp5apache2 and none of the candidates passed a file format test
*** using a file magic. Last file checked: 
/cygdrive/c/wamp/php//libphp5apache2.dll

*** Warning: libtool could not satisfy all declared inter-library
*** dependencies of module xapian.  Therefore, libtool will create
*** a static module, that should work as long as the dlopening
*** application is linked with the -dlopen flag.
ar cru .libs/xapian.a .libs/xapian_wrap.o
ranlib .libs/xapian.a
creating xapian.la

If "file" isn't available on cygwin by default, I feel it would be better to
say so rather than to say that a (probably valid) library failed the file magic
test...

Also, I have AC_DISABLE_STATIC in configure.ac, so I'm slightly suprised that
libtool falls back to building a static library here.  Is that supposed to
happen?

Cheers,
    Olly