[FS#1091] libiconv-full undefined reference compile-time linking error for x86/_64 using GCC7 Musl

[LEDE Bugs]

The following task has a new comment added:

FS#1091 - libiconv-full undefined reference compile-time linking error for x86/_64 using GCC7 Musl
User who did this - harrylwc (harrylwc)

----------
add -std=gnu89 to package/libs/libiconv-full/Makefile

TARGET_CFLAGS += $(FPIC) -DUSE_DOS -std=gnu89

----------

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1091#comment3655