[PATCH] kbuild: fix header installation under fakechroot environment

[Richard Genoud <richard.genoud@gmail.com>]

Since commit fcc8487d477a ("uapi: export all headers under uapi
directories") fakechroot make bindeb-pkg fails, mismatching files for
directories:
touch: cannot touch 'usr/include/video/uvesafb.h/.install': Not a
directory

This due to a bug in fakechroot:
when using the function $(wildcard $(srcdir)/*/.) in a makefile, under a
fakechroot environment, not only directories but also files are
returned.

To circumvent that, we are using the functions:
$(sort $(dir $(wildcard $(srcdir)/*/))))

And thanks to Yamada Masahiro who figured out the right
filter-out/patsubst order !

Fixes: fcc8487d477a ("uapi: export all headers under uapi directories")
Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
---
 scripts/Makefile.headersinst | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.headersinst b/scripts/Makefile.headersinst
index ce753a408c56..c583a1e1bd3c 100644
--- a/scripts/Makefile.headersinst
+++ b/scripts/Makefile.headersinst
@@ -14,7 +14,15 @@ __headers:
 include scripts/Kbuild.include
 
 srcdir        := $(srctree)/$(obj)
-subdirs       := $(patsubst $(srcdir)/%/.,%,$(wildcard $(srcdir)/*/.))
+
+# When make is run under a fakechroot environment, the function
+# $(wildcard $(srcdir)/*/.) doesn't only return directories, but also regular
+# files. So, we are using a combination of sort/dir/wildcard which works
+# with fakechroot.
+subdirs       := $(patsubst $(srcdir)/%/,%,\
+		 $(filter-out $(srcdir)/,\
+		 $(sort $(dir $(wildcard $(srcdir)/*/)))))
+
 # caller may set destination dir (when installing to asm/)
 _dst          := $(if $(dst),$(dst),$(obj))