fix(cmake/modules): added compiler flags for gtest

Signed-off-by: Roberto Scolaro <roberto.scolaro21@gmail.com>

Author: therealbobo

cmake/modules/falcosecurity-libs.cmake

@@ -93,6 +93,15 @@ else()
   message(STATUS "No strlcpy found, will use local definition")
 endif()
 
+include(CheckCXXCompilerFlag)
+CHECK_CXX_COMPILER_FLAG("-std=c++14" COMPILER_SUPPORTS_CXX14)
+if(CREATE_TEST_TARGETS AND NOT WIN32 AND COMPILER_SUPPORTS_CXX14)
+	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
+	include(gtest)
+elseif(CREATE_TEST_TARGETS AND NOT COMPILER_SUPPORTS_CXX14)
+	message(FATAL_ERROR "Your compiler doesn't support c++14: cannot include gtest and create test targets.")
+endif()
+
 if(CMAKE_SYSTEM_NAME MATCHES "Linux")
   include(driver)
 endif()