Bug 775182 - Use readelf from the toolchain, using TOOLCHAIN_PREFIX. r=khuey

configure.in

@@ -3642,7 +3642,7 @@ if test -n "$MOZ_LINKER" -a -z "$MOZ_OLD_LINKER" -a "$OS_TARGET" = "Android"; th
     [echo 'int foo() { return 0; }' > conftest.cpp
      if AC_TRY_COMMAND(${CXX-g++} -o conftest${DLL_SUFFIX} $CXXFLAGS $DSO_LDOPTS $LDFLAGS conftest.cpp $LIBS 1>&5) &&
         test -s conftest${DLL_SUFFIX}; then
-       if readelf -d conftest${DLL_SUFFIX} | grep TEXTREL > /dev/null; then
+       if ${TOOLCHAIN_PREFIX}readelf -d conftest${DLL_SUFFIX} | grep TEXTREL > /dev/null; then
          ac_cv_crt_has_text_relocations=yes
        else
          ac_cv_crt_has_text_relocations=no
@@ -7208,7 +7208,7 @@ if test "$USE_ELF_HACK" = 1; then
         [echo "int main() {return 0;}" > conftest.${ac_ext}
          if AC_TRY_COMMAND(${CC-cc} -o conftest${ac_exeext} $LDFLAGS conftest.${ac_ext} $LIBS 1>&2) &&
             test -s conftest${ac_exeext}; then
-            if readelf -l conftest${ac_exeext} | grep GNU_RELRO > /dev/null; then
+            if ${TOOLCHAIN_PREFIX}readelf -l conftest${ac_exeext} | grep GNU_RELRO > /dev/null; then
                 LINK_WITH_PT_GNU_RELRO=yes
             else
                 LINK_WITH_PT_GNU_RELRO=no