build-sys: C++11 is only required for WebRTC support

Make C++11 support optional and explicitly check for gnu++11.

Stop the build only if no C++11 support has been found and WebRTC
support has been requested.

Fixes:
http://autobuild.buildroot.net/results/d89/d897a94a8b6a52eba03d04c24536f554a7643000

Signed-off-by: Romain Naour <romain.naour@gmail.com>

diff --git a/configure.ac b/configure.ac
index 7b484a93dc4697f37016de736f58f20f22211dc7..7fbecabbe721947a206a3f53f13f7c4e9ba488d5 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -84,7 +84,7 @@ AM_PROG_CC_C_O
 # Only required if you want the WebRTC canceller -- no runtime dep on
 # libstdc++ otherwise
 AC_PROG_CXX
-AX_CXX_COMPILE_STDCXX_11
+AX_CXX_COMPILE_STDCXX_11([ext],[optional])
 AC_PROG_GCC_TRADITIONAL
 AC_USE_SYSTEM_EXTENSIONS
 
@@ -1410,6 +1410,9 @@ fi
 AC_ARG_ENABLE([webrtc-aec],
     AS_HELP_STRING([--enable-webrtc-aec], [Enable the optional WebRTC-based echo canceller]))
 
+AS_IF([test "x$enable_webrtc_aec" = "xyes" && test "$HAVE_CXX11" = "0"],
+    [AC_MSG_ERROR([*** webrtc-audio-processing needs C++11 support])])
+
 AS_IF([test "x$enable_webrtc_aec" != "xno"],
     [PKG_CHECK_MODULES(WEBRTC, [ webrtc-audio-processing >= 0.2 ], [HAVE_WEBRTC=1], [HAVE_WEBRTC=0])],
     [HAVE_WEBRTC=0])