Simplify optimization flags, add MSVC flags

CMakeLists.txt

@@ -150,25 +150,12 @@ if (ENABLE_COVERAGE)
     message(FATAL_ERROR "Coverage analysis requires a debug build.")
   endif()
 else()
-  if (NOT MSVC)
-    set(CMAKE_C_FLAGS_DEBUG "-g -O2")
-    set(CMAKE_CXX_FLAGS_DEBUG "-g -O2")
-
-    check_c_compiler_flag("-Os" "CFLAG__Os")
-    check_cxx_compiler_flag("-Os" "CXXFLAG__Os")
-
-    if(CFLAG__Os)
-      set(CMAKE_C_FLAGS_RELEASE "-Os -DNDEBUG")
-    else()
-      set(CMAKE_C_FLAGS_RELEASE "-O3 -DNDEBUG")
-    endif()
-
-    if(CFLAG__Os)
-      set(CMAKE_CXX_FLAGS_RELEASE "-Os -DNDEBUG")
-    else()
-      set(CMAKE_CXX_FLAGS_RELEASE "-O3 -DNDEBUG")
-    endif()
-  endif()
+  set_compiler_specific_flags(
+    VARIABLE optimization_flags
+    GCCISH -O3 -DNDEBUG
+    MSVC /O2 /DNDEBUG)
+  global_add_compiler_flags(${optimization_flags})
+  unset(optimization_flags)
 endif()
 
 set_directory_properties(PROPERTIES INTERPROCEDURAL_OPTIMIZATION TRUE)