gnu: gpsbabel: Fix tests.

Qt prints a "Detected locale C with character encoding ANSI_X3.4-1968, which
is not UTF-8" warning message when UTF-8 locales are missing, which makes some
tests fail.

* gnu/packages/gps.scm (gpsbabel)[native-inputs]: Add
  '(libc-utf8-locales-for-target)'.

Change-Id: I3a28912ed07fb7623d6b010d40d7882ebddd52c9

gnu/packages/gps.scm

@@ -100,9 +100,22 @@ (define-public gpsbabel
               "-DGPSBABEL_WITH_SHAPELIB=pkgconfig"
               "-DGPSBABEL_WITH_ZLIB=pkgconfig")))
     (inputs
-     (list expat libusb libxkbcommon shapelib qt5compat qtbase qtserialport qttranslations zlib))
+     (list expat
+           libusb
+           libxkbcommon
+           qt5compat
+           qtbase
+           qtserialport
+           qttranslations
+           shapelib
+           zlib))
     (native-inputs
-     (list which pkg-config qttools libxml2 tzdata-for-tests)) ;'xmllint' needed for the KML tests
+     (list (libc-utf8-locales-for-target)
+           libxml2  ;'xmllint' needed for the KML tests
+           pkg-config
+           qttools
+           tzdata-for-tests
+           which))
     (home-page "https://www.gpsbabel.org/")
     (synopsis "Convert and exchange data with GPS and map programs")
     (description