Allow proper overriding of CXXFLAGS.

Author: skrah

CMakeLists.txt

@@ -140,15 +140,15 @@ else()
             set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -D_hypot=hypot -std=c++14 -g -fomit-frame-pointer -fstrict-aliasing -Wall -Wextra -Werror -Wno-missing-field-initializers")
         endif()
     else()
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -fomit-frame-pointer -fstrict-aliasing -fPIC -Wall -Wextra -Werror -Wno-missing-field-initializers")
+        set(DYND_CXX_FLAGS "-g -fomit-frame-pointer -fstrict-aliasing -fPIC -Wall -Wextra -Werror -Wno-missing-field-initializers")
     endif()
     if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
         if ("${CMAKE_CXX_COMPILER_VERSION}" VERSION_LESS 4.9)
             message(FATAL_ERROR "Only GCC 4.9 and later are supported by DyND. Found version ${CMAKE_CXX_COMPILER_VERSION}.")
         endif()
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14 -fmax-errors=20")
+        set(DYND_CXX_FLAGS "${DYND_CXX_FLAGS} -std=c++14 -fmax-errors=20")
     elseif("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++1y -ferror-limit=20 -Wdocumentation")
+        set(DYND_CXX_FLAGS "${DYND_CXX_FLAGS} -std=c++1y -ferror-limit=20 -Wdocumentation")
     endif()
 endif()
 
@@ -157,10 +157,12 @@ if(MSVC)
 else()
     set(CMAKE_BUILD_WITH_INSTALL_RPATH TRUE)
     if(APPLE)
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unused-parameter -Wno-unused-function -Wno-error")
+        set(DYND_CXX_FLAGS "${DYND_CXX_FLAGS} -Wno-unused-parameter -Wno-unused-function -Wno-error")
     else()
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-error")
+        set(DYND_CXX_FLAGS "${DYND_CXX_FLAGS} -Wno-error")
     endif()
+
+    set(CMAKE_CXX_FLAGS "${DYND_CXX_FLAGS} ${CMAKE_CXX_FLAGS}")
 endif()
 
 include_directories(