make it possible to do 'make -C sw/' even with builddir!=srcdir

The change in partial_build.mk assumes all the Makefile's using it
are in builddir/<module>/ , but that seems to be the case.

Change-Id: Iddc8fa2ec0842f181780f7491cf5a2244efd014a

autogen.sh

@@ -135,6 +135,13 @@ if ($src_path ne $build_path)
 {
     system ("ln -sf $src_path/configure.ac configure.ac");
     system ("ln -sf $src_path/g g");
+    my @modules = <$src_path/*/Makefile>;
+    foreach my $module (@modules)
+    {
+        my $dir = basename (dirname ($module));
+        mkdir ($dir);
+        system ("ln -sf $src_path/$dir/Makefile $dir/Makefile");
+    }
 }
 system ("$aclocal $aclocal_flags") && die "Failed to run aclocal";
 unlink ("configure");

solenv/gbuild/partial_build.mk

@@ -22,7 +22,7 @@ gb_Side:=host
 endif
 
 ifeq (,$(BUILDDIR))
-BUILDDIR := $(dir $(realpath $(lastword $(MAKEFILE_LIST))))../..
+BUILDDIR := $(dir $(abspath $(firstword $(MAKEFILE_LIST))))..
 endif
 
 ifeq ($(BUILD_TYPE),)