[sysprof] build: check for c++ compiler

[Christian Hergert <chergert src gnome org>]

commit 43e61fc40a65b17b1e4f75f75036c592fad9d235
Author: Christian Hergert <christian hergert me>
Date:   Wed Apr 13 22:50:15 2016 -0700

    build: check for c++ compiler
    
    We need this for abi::__cxx_demangle()

 configure.ac |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 676985a..99f57d8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -68,6 +68,7 @@ dnl Check for required programs
 dnl ***********************************************************************
 AX_COMPILER_FLAGS_CXXFLAGS
 AC_PROG_CC
+AC_PROG_CXX
 AC_PROG_INSTALL
 AX_CXX_COMPILE_STDCXX_0X
 AC_PATH_PROG([GLIB_GENMARSHAL],[glib-genmarshal])