[source] elfutils: Pass -Wno-unused-result to silence warnings as errors

[LEDE Commits]

jow pushed a commit to source.git, branch lede-17.01:
https://git.lede-project.org/a6e5943a2afa5ffe733b9df23a4ba510d11b33fc

commit a6e5943a2afa5ffe733b9df23a4ba510d11b33fc
Author: Florian Fainelli <f.fainelli at gmail.com>
AuthorDate: Mon May 22 16:08:57 2017 -0700

    elfutils: Pass -Wno-unused-result to silence warnings as errors
    
    elfutils turns on -Werror by default, and patch 100-musl-compat.patch
    changes how strerror_r is used and we no longer use the function's
    return value. This causes the following build error/warning to occur
    with glibc-based toolchains:
    
    dwfl_error.c: In function 'dwfl_errmsg':
    dwfl_error.c:158:18: error: ignoring return value of 'strerror_r',
    declared with attribute warn_unused_result [-Werror=unused-result]
           strerror_r (error & 0xffff, s, sizeof(s));
                      ^
    cc1: all warnings being treated as errors
    
    Fixing this would be tricky as there are two possible signatures for
    strerror_r (XSI and GNU), just turn off unused-result warnings instead.
    
    Signed-off-by: Florian Fainelli <f.fainelli at gmail.com>
    (cherry picked from commit 484f768dfa295d9fccd82c57cae00458f32b7182)
---
 package/libs/elfutils/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package/libs/elfutils/Makefile b/package/libs/elfutils/Makefile
index d764970..869513f 100644
--- a/package/libs/elfutils/Makefile
+++ b/package/libs/elfutils/Makefile
@@ -68,7 +68,7 @@ endif
 CONFIGURE_ARGS += \
 	--without-lzma
 
-TARGET_CFLAGS += -D_GNU_SOURCE
+TARGET_CFLAGS += -D_GNU_SOURCE -Wno-unused-result
 
 define Build/InstallDev
 	$(INSTALL_DIR) $(1)/usr/include