[gimp-macos-build] Fix volume icon path

[Alex Samorukov <asamorukov src gnome org>]

commit f6ccb32a53ec905fc4e4e19cef04dca7ba08bddd
Author: Oleksii Samorukov <oleksii_samorukov mckinsey com>
Date:   Wed Oct 30 13:27:13 2019 +0100

    Fix volume icon path

 package/build.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/package/build.sh b/package/build.sh
index 5958456..f3144c7 100755
--- a/package/build.sh
+++ b/package/build.sh
@@ -130,7 +130,7 @@ cd create-dmg
 
 ./create-dmg \
 --volname "GIMP 2.10 Install" \
---volicon "/Applications/GIMP-2.10.app/Contents/Resources/gimp.icns" \
+--volicon "$PACKAGE_DIR/Contents/Resources/gimp.icns" \
 --background "../gimp-dmg.png" \
 --window-pos 1 1 \
 --icon "GIMP-2.10.app" 190 360 \