build: use cmake to pass -std=c++11

Rather than manually checking for support for the spelling of the C++
standard, indicate to CMake that we require that the compiler support
C++11 and that we compile without the GNU extensions.  This simplifies
the flags handling in libc++abi itself by relying on CMake to translate
the flag and add it as appropriate.

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@305175 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index d4a68fc..ff47ed3 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -111,6 +111,12 @@
 add_library(cxxabi_objects OBJECT ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
 set_target_properties(cxxabi_objects
                       PROPERTIES
+                        CXX_EXTENSIONS
+                          OFF
+                        CXX_STANDARD
+                          11
+                        CXX_STANDARD_REQUIRED
+                          ON
                         COMPILE_FLAGS
                           "${LIBCXXABI_COMPILE_FLAGS}"
                         POSITION_INDEPENDENT_CODE
@@ -124,6 +130,12 @@
   target_link_libraries(cxxabi_shared ${LIBCXXABI_LIBRARIES})
   set_target_properties(cxxabi_shared
                         PROPERTIES
+                          CXX_EXTENSIONS
+                            OFF
+                          CXX_STANDARD
+                            11
+                          CXX_STANDARD_REQUIRED
+                            ON
                           LINK_FLAGS
                             "${LIBCXXABI_LINK_FLAGS} ${LIBCXXABI_SHARED_LINK_FLAGS}"
                           OUTPUT_NAME
@@ -143,6 +155,12 @@
   target_link_libraries(cxxabi_static ${LIBCXXABI_LIBRARIES})
   set_target_properties(cxxabi_static
                         PROPERTIES
+                          CXX_EXTENSIONS
+                            OFF
+                          CXX_STANDARD
+                            11
+                          CXX_STANDARD_REQUIRED
+                            ON
                           LINK_FLAGS
                             "${LIBCXXABI_LINK_FLAGS}"
                           OUTPUT_NAME