package/poppler: set g-ir-scanner/g-ir-compiler paths

The g-ir-scanner/g-ir-compiler paths don't always get picked up
properly by cmake.

Fixes:
[ 98%] Linking CXX shared library libpoppler-glib.so
[ 98%] Built target poppler-glib
[ 98%] Generating Poppler-0.18.gir
/bin/sh: 1: /home/buildroot/buildroot/output/per-package/poppler/host/aarch64-buildroot-linux-gnu/sysroot/home/buildroot/buildroot/output/per-package/poppler/host/bin/../aarch64-buildroot-linux-gnu/sysroot/usr/lib/pkgconfig/../../bin/g-ir-scanner: not found

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/poppler/poppler.mk

@@ -44,7 +44,10 @@ endif
 
 ifeq ($(BR2_PACKAGE_GOBJECT_INTROSPECTION),y)
 POPPLER_DEPENDENCIES += gobject-introspection
-POPPLER_CONF_OPTS += -DENABLE_GOBJECT_INTROSPECTION=ON
+POPPLER_CONF_OPTS += \
+	-DENABLE_GOBJECT_INTROSPECTION=ON \
+	-DINTROSPECTION_SCANNER=$(STAGING_DIR)/usr/bin/g-ir-scanner \
+	-DINTROSPECTION_COMPILER=$(STAGING_DIR)/usr/bin/g-ir-compiler
 else
 POPPLER_CONF_OPTS += -DENABLE_GOBJECT_INTROSPECTION=OFF
 endif