Start with empty CMAKE_CXX_FLAGS and save it to the cache

Author: michaelbautin

CMakeLists.txt

@@ -138,6 +138,7 @@ string(STRIP "${CMAKE_CXX_FLAGS_RELWITHDEBINFO}" CMAKE_CXX_FLAGS_RELWITHDEBINFO)
 set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO}"
     CACHE STRING "Flags for RelWithDebInfo configuration." FORCE)
 
+set(CMAKE_CXX_FLAGS "")
 if(HNSWLIB_EXAMPLES)
     message("Building examples and tests")
     message("System architecture: ${CMAKE_HOST_SYSTEM_PROCESSOR}")
@@ -173,7 +174,7 @@ if(HNSWLIB_EXAMPLES)
                 set(${FLAGS_VAR} "${${FLAGS_VAR}}" CACHE STRING
                     "Flags for ${config} configuration." FORCE)
             endforeach()
-            string(REPLACE "/EHsc" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+            # string(REPLACE "/EHsc" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
         endif()
         add_cxx_flags(/O2 /W1 /openmp)
     endif()
@@ -243,3 +244,8 @@ if(HNSWLIB_EXAMPLES)
         endif()
     endforeach()
 endif()
+
+# Persist CMAKE_CXX_FLAGS in the cache for debuggability.
+string(STRIP "${CMAKE_CXX_FLAGS}" CMAKE_CXX_FLAGS)
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}"
+    CACHE STRING "Flags used by the CXX compiler during all build types." FORCE)