Switch to gnu++11 for spirv-llvm.

This library depends on a snapshot of LLVM that only works with C++11.

Bug: http://b/111067277
Test: Build with default cpp_std as C++17.
Change-Id: I00643842c5f4b47464709c7ff232f287e15586d0
diff --git a/lib/SPIRV/Android.bp b/lib/SPIRV/Android.bp
index a6cac53..959074a 100644
--- a/lib/SPIRV/Android.bp
+++ b/lib/SPIRV/Android.bp
@@ -87,6 +87,7 @@
         "-Werror",
         "-Wno-unused-parameter",
     ],
+    cpp_std: "gnu++11",
 
     clang_cflags: [
         // Temporarily suppress the warnings http://b/37867503
diff --git a/tools/llvm-spirv/Android.bp b/tools/llvm-spirv/Android.bp
index 2ad2c93..0f36d5d 100644
--- a/tools/llvm-spirv/Android.bp
+++ b/tools/llvm-spirv/Android.bp
@@ -53,6 +53,7 @@
         "-Werror",
         "-Wno-unused-parameter",
     ],
+    cpp_std: "gnu++11",
 
     product_variables: {
         unbundled_build: {