external/boringssl: Sync to aa2485.

This includes the following changes:

https://boringssl.googlesource.com/boringssl/+log/171b5403ee767fa0f3aecd377867db6533c3eb8f..aa24851515d6280aa1d6a8b1548fe74691df3136

Bug: 29744850
Change-Id: Id4e4a9e7a19c2f0badbaead2c39a51037ba182ed
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index bd7f432..050ba97 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -31,9 +31,9 @@
 endif()
 
 if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-  set(C_CXX_FLAGS "-Wall -Werror -Wformat=2 -Wsign-compare -Wmissing-field-initializers -ggdb -fvisibility=hidden")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${C_CXX_FLAGS} -Wmissing-prototypes")
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x ${C_CXX_FLAGS} -Wmissing-declarations")
+  set(C_CXX_FLAGS "-Wall -Werror -Wformat=2 -Wsign-compare -Wmissing-field-initializers -Wwrite-strings -ggdb -fvisibility=hidden -fno-common")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${C_CXX_FLAGS} -Wmissing-prototypes -Wold-style-definition -Wstrict-prototypes")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 ${C_CXX_FLAGS} -Wmissing-declarations")
 elseif(MSVC)
   set(MSVC_DISABLED_WARNINGS_LIST
       "C4100" # 'exarg' : unreferenced formal parameter