bug#15276: libtool.mk incorrectly resolves lt_sysroot?

[Hans Beckérus]

I am having problem running a SDK cross-compilation toolchain built
through Yocto.
After some digging I discovered that the root cause of the problem is
the fact that the sysroot is incorrectly resolved if --with-sysroot is
not specified when running configure. Actually in Yocto --with-sysroot
is replaced by -with-libtool-sysroot but that is irrelevant in this
case. I believe the error is in libtool.mk. Specifically the following
piece of code:

# _LT_WITH_SYSROOT
# ----------------
AC_DEFUN([_LT_WITH_SYSROOT],
[AC_MSG_CHECKING([for sysroot])
AC_ARG_WITH([sysroot],
[  --with-sysroot[=DIR] Search for dependent libraries within DIR
                        (or the compiler's sysroot if not specified).],
[], [with_sysroot=no])

dnl lt_sysroot will always be passed unquoted.  We quote it here
dnl in case the user passed a directory name.
lt_sysroot=
case ${with_sysroot} in #(
 yes)
   if test "$GCC" = yes; then
     lt_sysroot=`$CC --print-sysroot 2>/dev/null`
   fi
   ;; #(
 /*)
   lt_sysroot=`echo "$with_sysroot" | sed -e "$sed_quote_subst"`
   ;; #(
 no|'')
   ;; #(
 *)
   AC_MSG_RESULT([${with_sysroot}])
   AC_MSG_ERROR([The sysroot must be an absolute path.])
   ;;
esac

If --with-sysroot is *not* set it should be picked-up from the
compiler. But the switch statement above is wrong since the yes) and
no) cases are swapped.

Here is my configuration:

        host-triplet: arm-poky-linux-gnueabi
        shell: /bin/sh
        compiler: arm-poky-linux-gnueabi-gcc  -march=armv7-a
-mthumb-interwork -mfloat-abi=softfp -mtune=cortex-a9
--sysroot=/proj/nci_up/cpri_splitter/poky-chris/1.4+snapshot/sysroots/cortexa9-vfp-poky-linux-gnueabi
        compiler flags: -O2 -pipe -g -feliminate-unused-debug-types
        linker: arm-poky-linux-gnueabi-ld
--sysroot=/proj/nci_up/cpri_splitter/poky-chris/1.4+snapshot/sysroots/cortexa9-vfp-poky-linux-gnueabi
(gnu? yes)
        arm-poky-linux-gnueabi-libtool: (GNU libtool) 2.4.2
        automake: automake (GNU automake) 1.12.6
        autoconf: autoconf (GNU Autoconf) 2.69

Thanks.
Hans