package/swupdate: fix build issue with some toolchains

Add patch from upstream to fix build issue with some toolchains.

For some toolchains used in Buildroot (x86_64 and mips64) partial linking using
'ld' directly doesn't work well, as the 'ld' default emulation may not
necessarily be the correct one. Note, that the default emulation depends upon
how the linker was configured at build time. The leads to different kind of
build errors, like:

  * /usr/bin/i686-pc-linux-gnu-ld: Relocatable linking with relocations from
    format elf64-x86-64 (core/swupdate.o) to format elf32-i386 (core/built-in.o)
    is not supported.

  * /usr/bin/mips-linux-gnu-ld: handlers/raw_handler.o: endianness incompatible
    with that of the selected emulation

  * /usr/bin/mips64el-linux-ld: core/swupdate.o: ABI is incompatible with that
    of the selected

Linking with gcc will pass all the appropriate linker flags to the linker.
'-nostdlib' has to be added to ldflags-y to link properly without pulling in GCC
libs during partial linking. Note, for Kbuild ldflags-y is prefered over the
deprecated EXTRA_LDFLAGS.

Build config for x86_64:
  BR2_x86_64=y
  BR2_x86_corei7=y
  BR2_TOOLCHAIN_EXTERNAL=y
  BR2_TOOLCHAIN_EXTERNAL_CODESOURCERY_X86_201209=y

Runtime test:
  $ output/build/swupdate-2015.07/swupdate -v
  Swupdate v2015.07.0

  Licensed under GPLv2. See source distribution for detailed copyright notices.

  Registered handlers:
  	rawfile
	raw

Note, that a previous patch [1] had to be reverted [2] because ld does not take
gcc's constructor functions into account and so none of the handlers have been
registered at runtime.

Fixes:
http://autobuild.buildroot.net/results/de9/de920298075d32f3de83a0cfb7417846eb833425/
http://autobuild.buildroot.net/results/975/975915aa33005806e78260bae385cd4b3e359ca8/
http://autobuild.buildroot.net/results/c54/c54e7a2ea353d95d41a1e966de0dffa7b6ac432e/
http://autobuild.buildroot.net/results/019/0198596ebfed05ab86552b628da2274d55bf42ae/

and many more.

[1] https://patchwork.ozlabs.org/patch/532542/
[2] https://patchwork.ozlabs.org/patch/535408/

Cc: Bjørn Forsman <bjorn.forsman@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/swupdate/swupdate.hash

@@ -1,3 +1,4 @@
 # Locally calculated
 sha256	1410f8967aad0f4d3b4561110dbfb2c1f8e337bdc332f6b120f4995762c8bf6b  swupdate-2015.07.tar.gz
 sha256	6cffe115cad73c0d1095f7880b6d2b97fc12b7f7871f532e5b33717e863f03d7  5a5ef5909f5da5b2070d58ffaee924bb8e6a51e1.patch
+sha256	b97a107a0e4625337485b9bb118bc9a33fa0f2bfcb80475cff017940b5261238  f26577423eb65728fcd10f78f9978dd07d51dcb9.patch

package/swupdate/swupdate.mk

@@ -9,7 +9,8 @@ SWUPDATE_SITE = $(call github,sbabic,swupdate,$(SWUPDATE_VERSION))
 SWUPDATE_LICENSE = GPLv2+, MIT, Public Domain
 SWUPDATE_LICENSE_FILES = COPYING
 SWUPDATE_PATCH = \
-	https://github.com/sbabic/swupdate/commit/5a5ef5909f5da5b2070d58ffaee924bb8e6a51e1.patch
+	https://github.com/sbabic/swupdate/commit/5a5ef5909f5da5b2070d58ffaee924bb8e6a51e1.patch \
+	https://github.com/sbabic/swupdate/commit/f26577423eb65728fcd10f78f9978dd07d51dcb9.patch
 
 # swupdate bundles its own version of mongoose (version 3.8) and
 # lsqlite3 (version 0.8)