toolchain: mark uClibc 0.9.31 + locale + C++ as broken

It fails to build with:

ctype_members.cc: In constructor 'std::ctype_byname<_CharT>::ctype_byname(const char*, size_t) [with _CharT = char]':
ctype_members.cc:59: error: invalid use of incomplete type 'struct __uclibc_locale_struct'
/home/test/avr32-br/usr/avr32-unknown-linux-uclibc/sys-include/bits/uClibc_locale.h:85: error: forward declaration of 'struct __uclibc_locale_struct'
ctype_members.cc:60: error: invalid use of incomplete type 'struct __uclibc_locale_struct'
/home/test/avr32-br/usr/avr32-unknown-linux-uclibc/sys-include/bits/uClibc_locale.h:85: error: forward declaration of 'struct __uclibc_locale_struct'
ctype_members.cc:61: error: invalid use of incomplete type 'struct __uclibc_locale_struct'
/home/test/avr32-br/usr/avr32-unknown-linux-uclibc/sys-include/bits/uClibc_locale.h:85: error: forward declaration of 'struct __uclibc_locale_struct'
make[5]: *** [ctype_members.lo] Error 1

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

toolchain/toolchain-common.in

@@ -157,6 +157,7 @@ config BR2_GCC_CROSS_CXX
 config BR2_INSTALL_LIBSTDCPP
 	bool "Build/install c++ compiler and libstdc++?"
 	select BR2_GCC_CROSS_CXX
+	depends on !(BR2_avr32 && BR2_ENABLE_LOCALE && BR2_UCLIBC_VERSION_0_9_31)
 	help
 	  If you are building your own toolchain and want to build and install
 	  the C++ compiler and library then you need to enable this option.
@@ -164,6 +165,9 @@ config BR2_INSTALL_LIBSTDCPP
 	  support and you want to use the compiler / library then you need 
 	  to select this option.
 
+comment "C++ support broken in uClibc 0.9.31 with locale enabled"
+	depends on BR2_avr32 && BR2_ENABLE_LOCALE && BR2_UCLIBC_VERSION_0_9_31
+
 config BR2_TARGET_OPTIMIZATION
 	string "Target Optimizations"
 	default "-pipe"