[grilo-plugins] configure: don't override pkg-config if there's one already set

[Juan A. Suarez Romero <jasuarez src gnome org>]

commit 552278996ab1c677bf8c87719764845621066296
Author: Jonny Lamb <jonnylamb gnome org>
Date:   Wed Mar 13 17:43:13 2013 +0100

    configure: don't override pkg-config if there's one already set
    
    I wrote a wrapper pkg-config script for a specific build but
    grilo-pluins overrides my $PKG_CONFIG environment variable so my
    script isn't used.
    
    Signed-off-by: Jonny Lamb <jonnylamb gnome org>
    
    https://bugzilla.gnome.org/show_bug.cgi?id=695789

 configure.ac |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 2689d21..f8f3bfa 100644
--- a/configure.ac
+++ b/configure.ac
@@ -25,9 +25,11 @@ AC_PROG_CC
 AC_PROG_INSTALL
 AC_DISABLE_STATIC
 
-PKG_CONFIG="pkg-config"
-if test -n "$host" ; then
-       PKG_CONFIG=$host-$PKG_CONFIG
+if test -z "$PKG_CONFIG" ; then
+       PKG_CONFIG="pkg-config"
+       if test -n "$host" ; then
+               PKG_CONFIG=$host-$PKG_CONFIG
+       fi
 fi
 
 LT_PREREQ([2.2.6])