When cross compiling a target gcc, target flags may be used on the host

Configure identifies a number of warning flags (WARN_CFLAGS and
WARN_CXXFLAGS) from the $CC value.  The cross compiler may be different
from the host compiler and may not support the same set of flags.  This
leads to problems such as:

cc1plus: error: unrecognized command line option "-Wno-narrowing"
cc1plus: error: unrecognized command line option "-Wno-overlength-strings"

Work around this problem by removing the warning flags from the
BUILD_CXXFLAGS value, in a way similar to the BUILD_CFLAGS.

Upstream-Status: Pending

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>

Index: gcc-4.8.4/gcc/configure
===================================================================
--- gcc-4.8.4.orig/gcc/configure
+++ gcc-4.8.4/gcc/configure
@@ -17864,7 +17864,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 17853 "configure"
+#line 17867 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -17970,7 +17970,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 17959 "configure"
+#line 17973 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -26918,18 +26918,15 @@ $as_echo "#define TARGET_LIBC_PROVIDES_S
 fi
 
 # Test for <sys/sdt.h> on the target.
-
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking sys/sdt.h in the target C library" >&5
-$as_echo_n "checking sys/sdt.h in the target C library... " >&6; }
-have_sys_sdt_h=no
+#GCC_TARGET_TEMPLATE([HAVE_SYS_SDT_H])
+#AC_MSG_CHECKING(sys/sdt.h in the target C library)
+#have_sys_sdt_h=no
 #if test -f $target_header_dir/sys/sdt.h; then
 #  have_sys_sdt_h=yes
-#
-#$as_echo "#define HAVE_SYS_SDT_H 1" >>confdefs.h
-#
+#  AC_DEFINE(HAVE_SYS_SDT_H, 1,
+#            [Define if your target C library provides sys/sdt.h])
 #fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $have_sys_sdt_h" >&5
-$as_echo "$have_sys_sdt_h" >&6; }
+#AC_MSG_RESULT($have_sys_sdt_h)
 
 # Check if TFmode long double should be used by default or not.
 # Some glibc targets used DFmode long double, but with glibc 2.4