host: utils: Fixed python script paths under utils for windows

When uhd_usrp_probe is executed with incompatible UHD and FPGA images,
we get the expected incompat error. The problem is that on windows,
this error messages prints an incorrect file path to uhd_images_downloader.py.
It mentions folder "bin" but the python script is located under "lib".

For example:
current behavior "C:\Program Files\UHD\bin\uhd\utils\uhd_images_downloader.py"
expected behavior "C:\Program Files\UHD\lib\uhd\utils\uhd_images_downloader.py"

This fix is addressed by updating find_utility() function. Since, the dll in
windows is present under /bin, the get_lib_path() returns this path and
not the /lib path. To get the correct path, get_lib_path() is replaced by
get_pkg_path() and the rest of the file path is contructed using /lib/.

host/lib/utils/paths.cpp

@@ -524,7 +524,14 @@ std::string uhd::find_image_path(
 
 std::string uhd::find_utility(const std::string& name)
 {
+#ifdef UHD_PLATFORM_WIN32
+    /* python scripts are present under /lib/uhd/utils but the function
+    get_lib_path() return path including /bin/. This is because dll is located under /bin/
+    Correcting this behavior by using get_pkg_path() and appending /lib/. */
+    return (fs::path(uhd::get_pkg_path()) / "lib" / "uhd" / "utils" / name).string();
+#else
     return fs::path(fs::path(uhd::get_lib_path()) / "uhd" / "utils" / name).string();
+#endif
 }
 
 std::string uhd::print_utility_error(const std::string& name, const std::string& args)