bc: Use correct path to 'ar'

bc's configure script does not check for the 'ar' tool, which causes bc
to always use 'ar' even if the environment contains an AR variable, for
example for cross-compilation.

Fix this by checking for ar using the automake macro AM_PROG_AR.

Signed-off-by: Clemens Lang <clemens.lang@bmw-carit.de>

meta/recipes-extended/bc/bc_1.06.bb

@@ -13,7 +13,8 @@ DEPENDS = "flex"
 PR = "r3"
 
 SRC_URI = "${GNU_MIRROR}/bc/bc-${PV}.tar.gz \
-           file://fix-segment-fault.patch "
+           file://fix-segment-fault.patch \
+           file://find-ar-using-automake.patch "
 
 SRC_URI[md5sum] = "d44b5dddebd8a7a7309aea6c36fda117"
 SRC_URI[sha256sum] = "4ef6d9f17c3c0d92d8798e35666175ecd3d8efac4009d6457b5c99cea72c0e33"

meta/recipes-extended/bc/files/find-ar-using-automake.patch

@@ -0,0 +1,20 @@
+configure.in: Find AR using automake
+
+The configure script does not check for the 'ar' tool, which causes bc to
+always use 'ar' even if the environment contains an AR variable, for example
+for cross-compilation.
+
+Fix this by checking for ar using the automake macro AM_PROG_AR.
+
+Upstream-Status: Pending
+Signed-off-by: Clemens Lang <clemens.lang@bmw-carit.de>
+--- bc-1.06/configure.in.orig	2016-08-22 16:59:56.200916886 +0200
++++ bc-1.06/configure.in	2016-08-22 17:00:04.972499574 +0200
+@@ -18,6 +18,7 @@
+ AC_PROG_INSTALL
+ AC_PROG_RANLIB
+ AC_PROG_MAKE_SET
++AM_PROG_AR
+
+ AC_CHECK_HEADERS(stdarg.h stddef.h stdlib.h string.h limits.h unistd.h lib.h)
+ AC_C_CONST