tzdata: enable cross-compilation for Windows

  * Additional make flags are needed since some functions do not exist
    or have different names or parameters on Windows.

  * When compiling for Windows, GCC implicitly adds a `.exe` suffix to
    the output file name. A patch is needed for the `install` target
    to locate and install the correct files.

  * The tzdata Makefile contains `zic` and `ZIC` variables. The former
    refers to the path of the program to execute, while the latter
    invokes the former with additional arguments (it is defined as
    `ZIC=$(zic) $(ZFLAGS)`, `ZFLAGS` is normally empty).

    Previously, `ZIC` was overridden, potentially loosing `ZFLAGS`
    arguments. This commit changes it to override `zic` instead.

  * The `zic` program is built and installed as part of the package and
    also executed during the build to translate time-related files. When
    cross-compiling it means that two executables need to be compiled:
    one to get installed and run on the host platform, and another to
    run on the build platform. Instead of renaming files and building a
    temporary executable for the build platform, this commit references
    the build platform's `tzdata.bin` package and runs its `zic`
    program.

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