[source] libiconv-full: fix compile-time linking error GCC7

[LEDE Commits]

hauke pushed a commit to source.git, branch master:
https://git.lede-project.org/e80ab48777d83d8c24fcd397a85649f08b6b5f87

commit e80ab48777d83d8c24fcd397a85649f08b6b5f87
Author: Jake Staehle <jacob at staehle.us>
AuthorDate: Tue Oct 24 13:09:37 2017 -0500

    libiconv-full: fix compile-time linking error GCC7
    
    LEDE Flyspray Task 1091:
    Fix libiconv-full 'undefined reference' compile linker error using GCC7 Musl
    Tested with targets x86 (i386 and x86_64)
    Addition of CFLAGS "std=gnu89" fixes the linker issues, credit to harrylwc
    Issue found with 'minidlna' package, which depends on 'libiconv-full'
    Error in compile log:
    ../lib/.libs/libiconv.so: undefined reference to `aliases_lookup'
    ../lib/.libs/libiconv.so: undefined reference to `aliases2_lookup'
    collect2: error: ld returned 1 exit status
    Makefile:64: recipe for target 'iconv_no_i18n' failed
    
    Signed-off-by: Jake Staehle <jacob at staehle.us>
---
 package/libs/libiconv-full/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package/libs/libiconv-full/Makefile b/package/libs/libiconv-full/Makefile
index 9776711..ac7bfdd 100644
--- a/package/libs/libiconv-full/Makefile
+++ b/package/libs/libiconv-full/Makefile
@@ -51,7 +51,7 @@ define Package/iconv
   TITLE+= utility
 endef
 
-TARGET_CFLAGS += $(FPIC) -DUSE_DOS
+TARGET_CFLAGS += $(FPIC) -DUSE_DOS -std=gnu89
 
 CONFIGURE_ARGS += \
 	--enable-shared \