gallium/auxiliary: Fix Autotools on Android (v2)

Problem 1: u_debug_stack_android.cpp transitively included
"pipe/p_compiler.h", but src/gallium/include was missing from the C++
include path.

Problem 2: Add -std=c++11 to AM_CXXFLAGS. Android's libbacktrace headers
require C++11, but the Android toolchain (at least in the Chrome OS SDK)
does not enable C++11 by default.

v2: Add -std=c++11.

Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Cc: Eric Engestrom <eric.engestrom@intel.com>

src/gallium/auxiliary/Makefile.am

@@ -13,6 +13,7 @@ AM_CFLAGS = \
 	$(MSVC2013_COMPAT_CFLAGS)
 
 AM_CXXFLAGS = \
+	$(GALLIUM_CFLAGS) \
 	$(VISIBILITY_CXXFLAGS) \
 	$(MSVC2013_COMPAT_CXXFLAGS)
 
@@ -22,6 +23,10 @@ libgallium_la_SOURCES = \
 	$(GENERATED_SOURCES)
 
 if HAVE_PLATFORM_ANDROID
+# Android's libbacktrace headers required C++11, but the Android toolchain (at
+# least in the Chrome OS SDK) does not enable C++11 by default.
+AM_CXXFLAGS += $(CXX11_CXXFLAGS)
+
 libgallium_la_SOURCES += util/u_debug_stack_android.cpp
 endif
 
@@ -41,7 +46,6 @@ AM_CFLAGS += \
 	$(LLVM_CFLAGS)
 
 AM_CXXFLAGS += \
-	$(GALLIUM_CFLAGS) \
 	$(LLVM_CXXFLAGS)
 
 libgallium_la_SOURCES += \