Enable compilation of libc++ same way as uClibc++

libxx/Kconfig

@@ -38,6 +38,36 @@ config CXX_NEWLONG
 		C++ library routines because the NuttX size_t might not have
 		the same underlying type as your toolchain's size_t.
 
+
+comment "LLVM C++ Library (libcxx)"
+
+config LIBCXX
+	bool "Build LLVM libcxx (must be installed)"
+	default n
+	---help---
+		If you have installed libcxx into the NuttX source try, then it can
+		be built by selecting this option.  See the README.txt file in the
+		libcxx packet for information on installing libcxx.
+
+if LIBCXX
+
+config LIBCXX_EXCEPTION
+	bool "Enable Exception Suppport"
+	default y
+
+config LIBCXX_IOSTREAM_BUFSIZE
+	int "IO Stream Buffer Size"
+	default 32
+
+config LIBCXX_HAVE_LIBSUPCXX
+	bool "Have libsupc++ (required)"
+	default y
+	---help---
+		Select if your toolchain provides libsupc++.  This option is required
+		at present because the built-in libsupc++ support is incomplete.
+
+endif
+
 comment "uClibc++ Standard C++ Library"
 
 config UCLIBCXX

libxx/Makefile

@@ -41,18 +41,18 @@ ASRCS =
 CSRCS =
 
 CXXSRCS  = libxx_cxapurevirtual.cxx libxx_eabi_atexit.cxx  libxx_cxa_atexit.cxx
-ifeq ($(CONFIG_UCLIBCXX_EXCEPTION),y)
+ifneq (,$(findstring y,$(CONFIG_UCLIBCXX_EXCEPTION) $(CONFIG_LIBCXX_EXCEPTION)))
 CXXSRCS += libxx__gnu_unwind_find_exidx.cxx
 endif
 
-# Some of the libxx/ files are not need if uClibc++ is installed because
+# Some of the libxx/ files are not need if uClibc++ or libcxx is installed
-# uClibx++ replaces them
+# because uClibx++ or libcxx will replaces them
 
-ifneq ($(CONFIG_UCLIBCXX),y)
+ifeq (,$(findstring y,$(CONFIG_UCLIBCXX) $(CONFIG_LIBCXX)))
 CXXSRCS += libxx_delete.cxx libxx_deletea.cxx libxx_new.cxx libxx_newa.cxx
 CXXSRCS += libxx_stdthrow.cxx libxx_cxa_guard.cxx
 else
-ifneq ($(UCLIBCXX_EXCEPTION),y)
+ifeq (,$(findstring y,$(CONFIG_UCLIBCXX_EXCEPTION) $(CONFIG_LIBCXX_EXCEPTION)))
 CXXSRCS += libxx_stdthrow.cxx
 endif
 endif
@@ -76,6 +76,10 @@ ifeq ($(CONFIG_UCLIBCXX),y)
 include uClibc++/Make.defs
 endif
 
+ifeq ($(CONFIG_LIBCXX),y)
+include libcxx/Make.defs
+endif
+
 # Object Files
 
 AOBJS = $(ASRCS:.S=$(OBJEXT))