FTBFS: qt5-webkit broken since bison-3.7.3

[pullmoll]

The update of bison-3.7.3 broke the qt5-webkit build. It seems to be related to the automagically chosen filename for the header files with defines, i.e. the -d option of bison. The newer bison's choice for a name is obviously not what the perl script expects.

I tried to patch Source/WebCore/css/makegrammar.pl to cure that - to no avail. Here's my patch:

--- Source/WebCore/css/makegrammar.pl   2020-04-14 00:51:51.000000000 +0200
+++ Source/WebCore/css/makegrammar.pl   2020-10-25 14:59:39.879927464 +0100
@@ -73,7 +73,6 @@
 }

 my $fileBase = File::Spec->join($outputDir, $filename);
-my @bisonCommand = ($bison, "-d", "-p", $symbolsPrefix, $grammarFilePath, "-o", "$fileBase.cpp");
+my @bisonCommand = ($bison, "--no-lines", "--defines=$fileBase.hpp", "-p", $symbolsPrefix, $grammarFilePath
, "-o", $fileBase.cpp);
-push @bisonCommand, "--no-lines" if $^O eq "MSWin32"; # Work around bug in bison >= 3.0 on Windows where it
 puts backslashes into #line directives.
 system(@bisonCommand) == 0 or die;

--- Source/WebCore/css/CSSGrammar.y.in  2020-04-14 00:51:51.000000000 +0200
+++ Source/WebCore/css/CSSGrammar.y.in  2020-10-25 15:35:20.818799854 +0100
@@ -21,7 +21,7 @@
  *
  */

-%pure-parser
+%define api.pure

 %parse-param { CSSParser* parser }
 %lex-param { CSSParser* parser }

Now the previously missing XPathGrammar.hpp is created yet the file CSSGrammar.h is still missing and the build fails with:

In file included from /builddir/qtwebkit-opensource-src-5.212/Source/WebCore/css/CSSAllInOne.cpp:69:
/builddir/qtwebkit-opensource-src-5.212/Source/WebCore/css/CSSParser.cpp:11161:10: fatal error: CSSGrammar.h
: No such file or directory
11161 | #include "CSSGrammar.h"
      |          ^~~~~~~~~~~~~~
compilation terminated.

Note: I also tried --defines=$fileBase.cpp.h which is an alternative name for the input file which is read and wrapped in makegrammar.pl a few lines below the patch. I also tried with and without changing the obsolete %pure-parser to %define api.pure.

If anyone has a better knowledge of bison/yacc and how to fix the perl script please help fixing this issue.