package/kmsxx: add patch to fix LTO support

The LTO support in the kmsxx package uses the host gcc-ar and gcc-ranlib
instead of the ones from the cross-toolchain. Add a patch that tries to
find the right one based on CMAKE_C_COMPILER.

Fixes:
http://autobuild.buildroot.net/results/16a/16a38a4277dd1152a5955d62cb92f85447791ef3

Possibly also fixes:
http://autobuild.buildroot.net/results/f3c/f3c48da3a9706cd366c0e0a96c3cd0ff959f2a78
(it fails later, possibly because an incompatible host ar)

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Samuel Martin <s.martin49@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/kmsxx/0001-Fix-LTO-support-for-cross-compilation.patch

@@ -0,0 +1,45 @@
+From 5da1f631bc753655ac94b08a6233eecd0d451327 Mon Sep 17 00:00:00 2001
+From: "Arnout Vandecappelle (Essensium/Mind)" <arnout@mind.be>
+Date: Fri, 26 Aug 2016 21:55:06 +0200
+Subject: [PATCH] Fix LTO support for cross-compilation.
+
+When cross-compiling, the ar and ranlib to be used for LTO are prefixed
+by the cross-tuple. gcc-ar and gcc-ranlib may not exist. Cfr.
+http://autobuild.buildroot.net/results/f3c/f3c48da3a9706cd366c0e0a96c3cd0ff959f2a78/
+
+Therefore, search for an appropriate lto-ar and lto-ranlib before
+enabling LTO.
+
+Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
+---
+Submitted upstream: https://github.com/tomba/kmsxx/pull/14
+---
+ CMakeLists.txt | 12 +++++++++---
+ 1 file changed, 9 insertions(+), 3 deletions(-)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index e5b5ea5..c61c81d 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -39,9 +39,15 @@ if (NOT ${U_CMAKE_BUILD_TYPE} MATCHES DEBUG)
+     CHECK_CXX_COMPILER_FLAG("-flto" HAS_LTO_FLAG)
+ 
+     if (HAS_LTO_FLAG)
+-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -flto")
+-        set(CMAKE_AR gcc-ar)
+-        set(CMAKE_RANLIB gcc-ranlib)
++        find_program(LTO_AR NAMES "${CMAKE_C_COMPILER}-ar" gcc-ar)
++        find_program(LTO_RANLIB NAMES "${CMAKE_C_COMPILER}-ranlib" gcc-ranlib)
++        if (LTO_AR AND LTO_RANLIB)
++            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -flto")
++            set(CMAKE_AR "${LTO_AR}")
++            set(CMAKE_RANLIB "${LTO_RANLIB}")
++        else()
++            message(STATUS "gcc-ar or gcc-ranlib not found, disabling LTO")
++        endif()
+     endif()
+ endif()
+ 
+-- 
+2.9.3
+