binutils: Cache gettext api version 1 and 2 support

Problem described here

https://lists.gnu.org/archive/html/bug-gettext/2015-11/msg00012.html

gettext does not detect the gettext support in libc
correctly if the libc is not glibc. Musl does support
the gettext version 1 and 2 of APIs

http://www.openwall.com/lists/musl/2015/04/16/3

tests in gettext.m4 however fail since it pokes at glibc
internal symbols to determine the gettext APIs
musl's implementaitons are done differenty so the
tests fail and hence it does not enable  the libc
implementation. Since we install the header from
libc it confuses the compilation and results in errors
like

libbfd.so: undefined reference to `libintl_dgettext'

see
http://savannah.gnu.org/bugs/?46436

binutils need these variables in make env since
binutils build system runs configure in the sub directories
during make step, so we need to pass these flags
in compile step in addition to configure step

(From OE-Core rev: 21bba0548463f277684cc52d23194ad6d7c17956)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/binutils/binutils_2.26.bb

@@ -10,6 +10,10 @@ EXTRA_OECONF += "--with-sysroot=/ \
                 --with-system-zlib \
                 "
 
+EXTRA_OEMAKE_append_libc-musl = "\
+                                 gt_cv_func_gnugettext1_libc=yes \
+                                 gt_cv_func_gnugettext2_libc=yes \
+                                "
 EXTRA_OECONF_class-native = "--enable-targets=all \
                              --enable-64-bit-bfd \
                              --enable-install-libiberty \