[five-or-more] Improve checks for appdata-validate and desktop-file-validate

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 54e756cc09017ac74d79e03c8532b89b801f1e11
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Fri Nov 1 08:22:47 2013 -0500

    Improve checks for appdata-validate and desktop-file-validate

 configure.ac     |    3 +++
 data/Makefile.am |    4 ++++
 2 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index f861d7e..1e35765 100644
--- a/configure.ac
+++ b/configure.ac
@@ -67,7 +67,10 @@ PKG_CHECK_MODULES(FIVE_OR_MORE, [
 ])
 
 AC_PATH_PROG(APPDATA_VALIDATE, appdata-validate)
+AM_CONDITIONAL([VALIDATE_APPDATA], [test -n "${APPDATA_VALIDATE}"])
+
 AC_PATH_PROG(DESKTOP_FILE_VALIDATE, desktop-file-validate)
+AM_CONDITIONAL([VALIDATE_DESKTOP_FILE], [test -n "${DESKTOP_FILE_VALIDATE}"])
 
 dnl ###########################################################################
 dnl Internationalization
diff --git a/data/Makefile.am b/data/Makefile.am
index 2c881c7..073fb59 100644
--- a/data/Makefile.am
+++ b/data/Makefile.am
@@ -43,7 +43,11 @@ CLEANFILES = \
        $(desktop_DATA)
 
 check-local: $(appdata_DATA) $(desktop_DATA)
+if VALIDATE_APPDATA
        $(APPDATA_VALIDATE) $(appdata_DATA)
+endif
+if VALIDATE_DESKTOP_FILE
        $(DESKTOP_FILE_VALIDATE) $(desktop_DATA)
+endif
 
 -include $(top_srcdir)/git.mk