build-system/glib-or-gtk: Build 'in-source' by default.

* guix/build-system/glib-or-gtk.scm (glib-or-gtk-build): Change to
'out-of-source? #f'.
* gnu/packages/audio.scm (audacity)[arguments]: Use the default 'out-of-source?'
setting.
* gnu/packages/libreoffice.scm (libreoffice): Likewise.

gnu/packages/audio.scm

@@ -413,11 +413,6 @@ (define-public audacity
              (substitute* "src/prefs/MidiIOPrefs.cpp"
                (("../../lib-src/portmidi/pm_common/portmidi.h") "portmidi.h"))
              #t)))
-       ;; The translation Makefile generation is performed improperly for
-       ;; out-of-tree builds.
-       ;; XXX This can be removed if the glib-or-gkt-build-system
-       ;; switches to #:out-of-source? #t. See <https://bugs.gnu.org/32887>.
-       #:out-of-source? #f
        ;; The test suite is not "well exercised" according to the developers,
        ;; and fails with various errors.  See
        ;; <http://sourceforge.net/p/audacity/mailman/message/33524292/>.

gnu/packages/libreoffice.scm

@@ -1018,9 +1018,6 @@ (define-public libreoffice
     (arguments
      `(#:tests? #f ; Building the tests already fails.
        #:make-flags '("build-nocheck") ; Do not build unit tests, which fails.
-       ;; XXX Remove this if glib-or-gtk-build-system changes to in-source-tree
-       ;; builds by default.
-       #:out-of-source? #f
        #:phases
          (modify-phases %standard-phases
            (add-before 'configure 'prepare-src

guix/build-system/glib-or-gtk.scm

@@ -112,7 +112,7 @@ (define* (glib-or-gtk-build store name inputs
                             (configure-flags ''())
                             ;; Disable icon theme cache generation.
                             (make-flags ''("gtk_update_icon_cache=true"))
-                            (out-of-source? #t)
+                            (out-of-source? #f)
                             (tests? #t)
                             (test-target "check")
                             (parallel-build? #t)