Do not hardcode C std to C99 or C++ std to C++11 if not set
OE compilers are using newer than these standards and absl needs C++14 minimum

Upstream-Status: Pending
Signed-off-by: Khem Raj <raj.khem@gmail.com>
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -46,16 +46,6 @@ set_property(CACHE OTBR_MDNS PROPERTY ST
 
 include("${PROJECT_SOURCE_DIR}/etc/cmake/options.cmake")
 
-if(NOT CMAKE_C_STANDARD)
-    set(CMAKE_C_STANDARD 99)
-    set(CMAKE_C_STANDARD_REQUIRED ON)
-endif()
-
-if(NOT CMAKE_CXX_STANDARD)
-    set(CMAKE_CXX_STANDARD 11)
-    set(CMAKE_CXX_STANDARD_REQUIRED ON)
-endif()
-
 set(CMAKE_CXX_EXTENSIONS OFF)
 set(CMAKE_EXE_LINKER_FLAGS "-rdynamic ${CMAKE_EXE_LINKER_FLAGS}")
 
@@ -63,6 +53,10 @@ if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
 	add_compile_options(-Wno-error=nonnull-compare)
 endif()
 
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 18.1)
+	add_compile_options(-Wno-error=vla-cxx-extension)
+endif()
+
 if (OTBR_COVERAGE AND CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
     message(STATUS "Coverage: ON")
     target_compile_options(otbr-config INTERFACE -g -O0 --coverage)