[gthumb] configure: Use ${PKG_CONFIG} instead of pkg-config

[Paolo Bacchilega <paobac src gnome org>]

commit be902984c8f255c49cd4ab795b882c7ec7a44c2c
Author: Quentin Glidic <sardemff7+git sardemff7 net>
Date:   Tue Sep 22 10:14:23 2015 +0200

    configure: Use ${PKG_CONFIG} instead of pkg-config
    
    Some use cases (e.g. cross-compiling) require a prefixed pkg-config
    
    https://bugzilla.gnome.org/show_bug.cgi?id=755390
    
    Signed-off-by: Quentin Glidic <sardemff7+git sardemff7 net>

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index db67766..9ace0e1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -199,7 +199,7 @@ if test x$enable_exiv2 = xyes ; then
                          exiv2 >= $EXIV2_REQUIRED,
                          [enable_exiv2=yes],
                          [enable_exiv2=no])
-       if pkg-config --atleast-version=0.20 exiv2; then
+       if ${PKG_CONFIG} --atleast-version=0.20 exiv2; then
                AC_DEFINE(HAVE_EXIV2_020, 1, [Have exiv2 0.20 or greater])
        fi
 fi