Android: Some Qt modules get broken install rules on Windows

This is reproducible e.g. when cross-compiling the Qt Purchasing API for Android on Windows, but it has also been reported for other external modules.

The Makefile gets the following in its "install_target":

install_target: first FORCE
[...]
        -$(INSTALL_PROGRAM) "..\..\lib\$(TARGET)" "D:$(INSTALL_ROOT)\releasetesting\5.3.0beta\5.3\android_armv7\lib\$(TARGET)"
        -$(SYMLINK) "$(TARGET)" "D:$(INSTALL_ROOT)\releasetesting\5.3.0beta\5.3\android_armv7\lib\$(TARGET0)"
        -$(SYMLINK) "$(TARGET)" "D:$(INSTALL_ROOT)\releasetesting\5.3.0beta\5.3\android_armv7\lib\$(TARGET1)"
        -$(SYMLINK) "$(TARGET)" "D:$(INSTALL_ROOT)\releasetesting\5.3.0beta\5.3\android_armv7\lib\$(TARGET2)"

The $(TARGET), which is libQt5FooBar.so.5.3.0, is correctly installed from "../../lib", but the subsequent rules for the symlinks try to get $(TARGET) from the current directory, and fail. On Android, the libQt5FooBar.so is the only one that matters, so applications using the module will fail on startup since this library is not found.