[gcr] build: Add easy way to run make when $srcdir != $builddir

[Stefan Walter <stefw src gnome org>]

commit 166a72d726d578f1550a8dd8610950c5a8b0b777
Author: Stef Walter <stefw gnome org>
Date:   Sat Feb 13 14:24:13 2016 +0100

    build: Add easy way to run make when $srcdir != $builddir

 autogen.sh              |    7 +++++++
 build/Makefile.redirect |    9 +++++++++
 2 files changed, 16 insertions(+), 0 deletions(-)
---
diff --git a/autogen.sh b/autogen.sh
index d5c782b..794e1c5 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -5,6 +5,7 @@ PKG_NAME="gcr"
 USE_GNOME2_MACROS=1
 REQUIRED_AUTOMAKE_VERSION=1.11
 
+olddir=`pwd`
 srcdir=`dirname $0`
 test -z "$srcdir" && srcdir=.
 
@@ -20,3 +21,9 @@ which gnome-autogen.sh || {
 }
 
 . gnome-autogen.sh
+
+# Put a redirect makefile here
+if [ ! -f $srcdir/Makefile ]; then
+    cat $srcdir/build/Makefile.redirect > $srcdir/Makefile
+    printf "\nREDIRECT = %s\n" "$(realpath $olddir)" >> $srcdir/Makefile
+fi
diff --git a/build/Makefile.redirect b/build/Makefile.redirect
new file mode 100644
index 0000000..db371eb
--- /dev/null
+++ b/build/Makefile.redirect
@@ -0,0 +1,9 @@
+# This redirects all make targets to builddir
+all:
+       $(MAKE) -C $(REDIRECT) all
+%:
+       $(MAKE) -C $(REDIRECT) $@
+ifeq ($(MAKEFLAGS), )
+JOBARG = -j4
+endif
+# REDIRECT=build