--- a/src/buildtools/config/functions.pri

+++ b/src/buildtools/config/functions.pri

@@ -1,5 +1,5 @@

 defineReplace(qtwebengine_extractCFlag) {

-    CFLAGS = $$QMAKE_CC $$QMAKE_CFLAGS

+    CFLAGS = $$QMAKE_CC $$QMAKE_CFLAGS $$QMAKE_CFLAGS_RELEASE

     OPTION = $$find(CFLAGS, $$1)

     OPTION = $$split(OPTION, =)

     PARAM = $$member(OPTION, 1)