Building QWebEngine fails with OpenSSL in include path

1) Qt fails to build with following errors:

../../../../../ext_qt/qtwebengine/src/3rdparty/chromium/third_party/boringssl/src/include/openssl/pool.h:38:16: error: expected constructor, destructor, or type conversion before ���CRYPTO_BUFFER_POOL���
 OPENSSL_EXPORT CRYPTO_BUFFER_POOL* CRYPTO_BUFFER_POOL_new(void);
 ^~~~~~~~~~~~~~~~~~
In file included from ../../../../../ext_qt/qtwebengine/src/3rdparty/chromium/content/browser/devtools/protocol/security_handler.cc:22:0:
../../../../../ext_qt/qtwebengine/src/3rdparty/chromium/net/cert/x509_util.h:110:27: error: expected primary-expression before ���)��� token
 STACK_OF(CRYPTO_BUFFER) * buffers);
 ^
../../../../../ext_qt/qtwebengine/src/3rdparty/chromium/net/cert/x509_util.h:110:27: error: ���STACK_OF��� was not declared in this scope
../../../../../ext_qt/qtwebengine/src/3rdparty/chromium/net/cert/x509_util.h:110:31: error: ���buffers��� was not declared in this scope

2) We've got CI system that builds Qt and the log can be seen here

https://binary-factory.kde.org/job/KMyMoney_Nightly_Appimage_Dependency_Build/33/consoleText

3) I build Qt by ExternalProject_Add (see attachment for exact configuration)

Whole build system can be seen here

https://cgit.kde.org/kmymoney.git/tree/3rdparty

and here

https://cgit.kde.org/kmymoney.git/tree/packaging/linux/appimage

4) Latest ICU, OpenSSL, and Zlib is built and installed to /home/appimage//appimage-workspace/deps/usr before Qt

5) I use OPENSSL_INCDIR, ICU_INCDIR, and ZLIB_INCDIR which all point to /home/appimage//appimage-workspace/deps/usr

6) Just before the error, there are two -I directives

-I/home/appimage/appimage-workspace/deps/usr/include -I/home/appimage/appimage-workspace/deps/usr/include

that are used before

-I../../../../../ext_qt/qtwebengine/src/3rdparty/chromium/third_party/boringssl/src/include

I think they are causing use of OpenSSL headers from /home/appimage/appimage-workspace/deps/usr/include instead of BoringSSL's headers. I think that causes the error.

7) There is no error in Qt build with -skip qtwebengine during configuration