When I try to upgrade glibc. I got the error when testing chromiumos-sdk.

https://uberchromegw.corp.google.com/i/chromiumos.tryserver/builders/chromiumos-sdk/builds/2013

It fails to build glibc-headers.

/var/tmp/portage/cross-mipsel-cros-linux-gnu/glibc-2.23-r2/work/glibc-2.23/configure --disable-sanity-checks --enable-hacker-mode --without-cvs --disable-werror --enable-bind-now --build=x86_64-pc-linux-gnu --host=mipsel-cros-linux-gnu --with-headers=/usr/mipsel-cros-linux-gnu/usr/include --prefix=/usr --with-bugurl=http://crbug.com/new --enable-add-ons=
configure: loading site script /usr/share/config.site
checking build system type... x86_64-pc-linux-gnu
checking host system type... mipsel-cros-linux-gnu
checking for mipsel-cros-linux-gnu-gcc... x86_64-pc-linux-gnu-gcc
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether x86_64-pc-linux-gnu-gcc accepts -g... yes
checking for gcc... gcc
checking for mipsel-cros-linux-gnu-readelf... mipsel-cros-linux-gnu-readelf
checking for mipsel-cros-linux-gnu-g++... no
checking for mipsel-cros-linux-gnu-c++... no
checking for mipsel-cros-linux-gnu-gpp... no
checking for mipsel-cros-linux-gnu-aCC... no
checking for mipsel-cros-linux-gnu-CC... no
checking for mipsel-cros-linux-gnu-cxx... no
checking for mipsel-cros-linux-gnu-cc++... no
checking for mipsel-cros-linux-gnu-cl.exe... no
checking for mipsel-cros-linux-gnu-FCC... no
checking for mipsel-cros-linux-gnu-KCC... no
checking for mipsel-cros-linux-gnu-RCC... no
checking for mipsel-cros-linux-gnu-xlC_r... no
checking for mipsel-cros-linux-gnu-xlC... no
checking for g++... g++
configure: WARNING: using cross tools not prefixed with host triplet
checking whether we are using the GNU C++ compiler... yes
checking whether g++ accepts -g... yes
checking whether g++ can link programs... yes
checking for sysdeps preconfigure fragments... aarch64 alpha arm hppa i386 m68k microblaze mips configure: error: Unable to determine ABI.
 * ERROR: cross-mipsel-cros-linux-gnu/glibc-2.23-r2::crossdev failed (configure phase):

When building libc-headers, there is no compiler yet. It chooses the host compiler instead. In the 

sysdeps/mips/preconfigure

It has the following script to test the ABI. Because at this time, the $CC is set to x86_64-pc-linux-gnu-gcc, so it could not find mips information from the compiler and the error happens.

case "$machine" in
mips*)
        abiflag=`$CC $CFLAGS $CPPFLAGS -E -dM -xc /dev/null | sed -n 's/^#define _MIPS_SIM \(.*\)/\1/p'`
        mips16flag=`$CC $CFLAGS $CPPFLAGS -E -dM -xc /dev/null | sed -n 's/^#define __mips16 \(.*\)/\1/p'`
        echo "$CC $CFLAGS $CPPFLAGS -E -dM -xc /dev/null | sed -n 's/^#define _MIPS_SIM \(.*\)/\1/p'"
        base_machine=mips
        if test "$abiflag" = "_ABIO32" ; then
                if test "$mips16flag" = "1" ; then
                        machine=mips/mips32/mips16
                else
                        machine=mips/mips32
                fi
        elif test "$abiflag" = "_ABIN32" ; then
                machine=mips/mips64/n32
        elif test "$abiflag" = "_ABI64" ; then
                machine=mips/mips64/n64
        else
                as_fn_error $? "Unable to determine ABI." "$LINENO" 5
        fi