pkg-config: strip system library paths reliably

pkg-config was skipping every other link flag due to a list manipulation bug,
backport a commit from git to fix this.

This will stop users of zlib.pc from inserting the sysroot directory indirectly
into builds.

(From OE-Core rev: df3ecaf86360a9c109b1b19bfa8a52890315bbdc)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/pkgconfig/pkgconfig-0.28/0001-Strip-system-library-directories-reliably.patch

@@ -0,0 +1,30 @@
+Upstream-Status: Backport (will be in 0.29)
+Signed-off-by: Ross Burton <ross.burton@intel.com>
+
+From ce1a2416ce0f0bd9a8a8a5caaf7dad20cda4d47d Mon Sep 17 00:00:00 2001
+From: Andrew Oakley <aoakley@espial.com>
+Date: Tue, 29 Apr 2014 13:14:35 +0100
+Subject: [PATCH] Strip system library directories reliably
+
+This loop was changed from a while loop to a for loop in commit
+9bf6277b, but the iterator is now advanced twice each time round the
+loop.
+---
+ pkg.c |    1 -
+ 1 file changed, 1 deletion(-)
+
+diff --git a/pkg.c b/pkg.c
+index 3697fec..c847c95 100644
+--- a/pkg.c
++++ b/pkg.c
+@@ -917,7 +917,6 @@ verify_package (Package *pkg)
+             }
+           system_dir_iter = system_dir_iter->next;
+         }
+-      iter = iter->next;
+     }
+   g_list_free (system_directories);
+ 
+-- 
+1.7.10.4
+

meta/recipes-devtools/pkgconfig/pkgconfig_0.28.bb

@@ -4,6 +4,7 @@ SRC_URI += " \
             file://pkg-config-native.in \
             file://fix-glib-configure-libtool-usage.patch \
             file://obsolete_automake_macros.patch \
+            file://0001-Strip-system-library-directories-reliably.patch \
            "
 
 SRC_URI[md5sum] = "aa3c86e67551adc3ac865160e34a2a0d"