Align windows package layout

[mara004]

For all non-windows platforms, the actual binary is in lib/.
For windows, it is in bin/, while lib/ contains a special pdfium.dll.lib file.
That's a bit unexpected/confusing and needs special handling by packagers.

How about putting both files in lib/ ?

[bblanchon]

As far as I remember this is the convention.
I just looked at CMake's documentation and it goes in the same way:

LIBRARY
Target artifacts of this kind include:

• Shared libraries, except
  • DLLs (these go to RUNTIME, see below),
  • on macOS when marked as FRAMEWORK (see below).

RUNTIME

• Target artifacts of this kind include:
  • Executables (except on macOS when marked as MACOSX_BUNDLE, see BUNDLE below);
  • DLLs (on all Windows-based systems including Cygwin; note that the accompanying import libraries are of kind ARCHIVE).

Target Type	GNUInstallDirs Variable	Built-In Default
RUNTIME	${CMAKE_INSTALL_BINDIR}	bin
LIBRARY	${CMAKE_INSTALL_LIBDIR}	lib
ARCHIVE	${CMAKE_INSTALL_LIBDIR}	lib
PRIVATE_HEADER	${CMAKE_INSTALL_INCLUDEDIR}	include
PUBLIC_HEADER	${CMAKE_INSTALL_INCLUDEDIR}	include
FILE_SET (type HEADERS)	${CMAKE_INSTALL_INCLUDEDIR}	include

[mara004]

Indeed, it is also for conda:

Unix-style packages on Windows, which are usually statically linked to executables, are built in a special Library directory under the build prefix. The environment variables listed in the following table are defined only on Windows.

CYGWIN_PREFIX	Same as PREFIX, but as a Unix-style path, such as /cygdrive/c/path/to/prefix.
LIBRARY_BIN	<build prefix>\Library\bin.
LIBRARY_INC	<build prefix>\Library\include.
LIBRARY_LIB	<build prefix>\Library\lib.
LIBRARY_PREFIX	<build prefix>\Library.
SCRIPTS	<build prefix>\Scripts.

[mara004]

Since this is the convention I think it's fine as-is. Just something packagers need to bear in mind.