qt5-qtwebengine 15.4.2_1 fails to build. Mac OS Catalina 10.15.6

[NeilBowles]

Hi

I'm having problems installing the py38-spyder port. The install proceeds normally but then fails when it attempts to install and build the latest version of qt5-qtwebengine. After a "clean" I've attempted to install just the qt5-qtwebengine port and this also fails. The final part of the log that generates the fatal build error is below, any help with a fix is greatly appreciated.

The problem line seems to be:

:info:build [16311/17617] ../../../../../../../../../../../../Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -MMD -MF 
:info:build FAILED: obj/third_party/blink/renderer/core/core_generated/core_generated_jumbo_11.o 
:info:build ../../../../../../../../../../../../Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -MMD -MF o
:info:build /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_aqua_qt5/qt5-qtwebengine/work/qtwebengine-everywhere-src-5.14.2/src/core/release/gen/third_party/blink/renderer/core/xpath_grammar.cc:124:10: fatal error: 'xpath_grammar.hh' file not found
:info:build #include "xpath_grammar.hh"
:info:build          ^~~~~~~~~~~~~~~~~~
:info:build 1 error generated.

[NeilBowles]

More detailed error log.

[NeilBowles]

Seems to be a problem with bison 3.7? ​https://bugs.gentoo.org/734356

[Schamschula (Marius Schamschula)]

See: ​https://trac.macports.org/ticket/60978

[mf2k (Frank Schima)]

#60978