[gnome-sdk-images] Dont remove the sdk directory

[Tristan Van Berkom <tvb src gnome org>]

commit a438e22716301b3a6368fa180e759183f0bac976
Author: Tristan Van Berkom <tristan vanberkom codethink co uk>
Date:   Thu Jun 2 21:05:11 2016 +0900

    Dont remove the sdk directory
    
    When building manually it can be useful to debug, and
    when building automatically we use it to check if anything
    was actually built and then remove it manually.

 Makefile |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)
---
diff --git a/Makefile b/Makefile
index 088967e..51a9016 100644
--- a/Makefile
+++ b/Makefile
@@ -25,12 +25,10 @@ define subst-metadata
 endef
 
 all: ${REPO} $(patsubst %,%.in,$(SUBST_FILES))
-       rm -rf sdk
        $(call subst-metadata)
        flatpak-builder --force-clean --ccache --require-changes --repo=${REPO} --arch=${ARCH} \
                         --subject="build of org.gnome.Sdk, `date`" \
                         ${EXPORT_ARGS} sdk org.gnome.Sdk.json
-       rm -rf sdk
 
 ${REPO}:
        ostree  init --mode=archive-z2 --repo=${REPO}