Respect user CXXFLAGS setting.

--- a/src/CMakeLists.txt	2019-05-06 15:09:19.010755505 +0200
+++ b/src/CMakeLists.txt	2019-05-06 15:14:11.668510627 +0200
@@ -307,28 +307,28 @@
 endif(READLINE_FOUND)
 
 # set platform specific compiler flags
-if (BuildFor0ld_X86)
-    set (OurCxxFlags ${BuildOptions_X86})
-else (BuildFor0ld_X86)
-    if (BuildForAMD_X86_64)
-        set (OurCxxFlags ${BuildOptions_X86_64AMD})
-    else (BuildForAMD_X86_64)
-        if (BuildForCore2_X86_64)
-            set (OurCxxFlags ${BuildOptions_X86_64Core2})
-        else (BuildForCore2_X86_64)
-            if (BuildForNEON)
-                set (OurCxxFlags ${BuildOptions_NEON})
-            else (BuildForNEON)
-                if (BuildForThisCPU)
-                    set (OurCxxFlags ${BuildOptionsThisCPU})
-                else (BuildForThisCPU)
-                    set (OurCxxFlags ${BuildOptionsBasic})
-                endif (BuildForThisCPU)
-            endif (BuildForNEON)
-        endif (BuildForCore2_X86_64)
-    endif (BuildForAMD_X86_64)
-endif (BuildFor0ld_X86)
-set (CMAKE_CXX_FLAGS "${OurCxxFlags} ${CMAKE_CXX_FLAGS}")
+# if (BuildFor0ld_X86)
+#     set (OurCxxFlags ${BuildOptions_X86})
+# else (BuildFor0ld_X86)
+#     if (BuildForAMD_X86_64)
+#         set (OurCxxFlags ${BuildOptions_X86_64AMD})
+#     else (BuildForAMD_X86_64)
+#         if (BuildForCore2_X86_64)
+#             set (OurCxxFlags ${BuildOptions_X86_64Core2})
+#         else (BuildForCore2_X86_64)
+#             if (BuildForNEON)
+#                 set (OurCxxFlags ${BuildOptions_NEON})
+#             else (BuildForNEON)
+#                 if (BuildForThisCPU)
+#                     set (OurCxxFlags ${BuildOptionsThisCPU})
+#                 else (BuildForThisCPU)
+#                     set (OurCxxFlags ${BuildOptionsBasic})
+#                 endif (BuildForThisCPU)
+#             endif (BuildForNEON)
+#         endif (BuildForCore2_X86_64)
+#     endif (BuildForAMD_X86_64)
+# endif (BuildFor0ld_X86)
+# set (CMAKE_CXX_FLAGS "${OurCxxFlags} ${CMAKE_CXX_FLAGS}")
 
 if (BuildForDebug)
     set (CMAKE_BUILD_TYPE "Debug")
@@ -330,8 +330,8 @@
     message (STATUS "DEBUG Build, flags: ${CMAKE_CXX_FLAGS} ${CMAKE_CXX_FLAGS_DEBUG}")
 else (BuildForDebug)
     set (CMAKE_BUILD_TYPE "Release")
-    set (CMAKE_CXX_FLAGS_RELEASE ${BuildOptionsRelease})
-    message (STATUS "RELEASE Build, flags: ${CMAKE_CXX_FLAGS} ${CMAKE_CXX_FLAGS_RELEASE}")
+    # set (CMAKE_CXX_FLAGS_RELEASE ${BuildOptionsRelease})
+    message (STATUS "RELEASE Build, flags: ${CMAKE_CXX_FLAGS}")
 endif (BuildForDebug)
 
 configure_file(