dev-qt/qtwebengine: fix build with >=bison-3.7

Backport commit from Qt upstream [1].

1. https://code.qt.io/cgit/qt/qtwebengine-chromium.git/commit/?h=80-based&id=1a53f599

Reported-by: Toralf Förster <toralf@gentoo.org>
Thanks-to: YOSHIOKA Takuma <lo73741824@hard-wi.red>
Closes: https://bugs.gentoo.org/734356
Package-Manager: Portage-3.0.3, Repoman-3.0.0
Signed-off-by: Jimi Huotari <chiitoo@gentoo.org>
Closes: https://github.com/gentoo/gentoo/pull/17171
Signed-off-by: Andreas Sturmlechner <asturm@gentoo.org>

dev-qt/qtwebengine/files/qtwebengine-5.15.0-bison-3.7-build.patch

@@ -0,0 +1,54 @@
+From 1a53f5995697f5ac6fd501dbdc0ee39c9488ee66 Mon Sep 17 00:00:00 2001
+From: Allan Sandfeld Jensen <allan.jensen@qt.io>
+Date: Fri, 14 Aug 2020 16:38:48 +0200
+Subject: Fix bison 3.7
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Do a replace run inspired by newer versions of the script.
+
+Fixes: QTBUG-86018
+Change-Id: Ib1dc771e22a662aff0fae842d135ad58fad08bc1
+Reviewed-by: Michael Brüning <michael.bruning@qt.io>
+---
+ .../blink/renderer/build/scripts/rule_bison.py        | 19 +++++++++++++++++++
+ 1 file changed, 19 insertions(+)
+
+diff --git a/chromium/third_party/blink/renderer/build/scripts/rule_bison.py b/chromium/third_party/blink/renderer/build/scripts/rule_bison.py
+index f75e25fd23f..7e0767e951a 100755
+--- a/src/3rdparty/chromium/third_party/blink/renderer/build/scripts/rule_bison.py
++++ b/src/3rdparty/chromium/third_party/blink/renderer/build/scripts/rule_bison.py
+@@ -45,6 +45,19 @@ from utilities import abs
+ 
+ from blinkbuild.name_style_converter import NameStyleConverter
+ 
++def modify_file(path, prefix_lines, suffix_lines, replace_list=[]):
++    prefix_lines = map(lambda s: s + '\n', prefix_lines)
++    suffix_lines = map(lambda s: s + '\n', suffix_lines)
++    with open(path, 'r') as f:
++        old_lines = f.readlines()
++    for i in range(len(old_lines)):
++        for src, dest in replace_list:
++            old_lines[i] = old_lines[i].replace(src, dest)
++    new_lines = prefix_lines + old_lines + suffix_lines
++    with open(path, 'w') as f:
++        f.writelines(new_lines)
++
++
+ assert len(sys.argv) == 4 or len(sys.argv) == 5
+ 
+ inputFile = abs(sys.argv[1])
+@@ -115,3 +128,9 @@ print >>outputHFile, '#define %s' % headerGuard
+ print >>outputHFile, outputHContents
+ print >>outputHFile, '#endif  // %s' % headerGuard
+ outputHFile.close()
++
++common_replace_list = [(inputRoot + '.hh',
++                        inputRoot + '.h')]
++modify_file(
++    outputCpp, [], [],
++    replace_list=common_replace_list)
+-- 
+cgit v1.2.1
+

dev-qt/qtwebengine/qtwebengine-5.15.0.ebuild

@@ -85,6 +85,7 @@ PATCHES=(
 	"${FILESDIR}/${P}-disable-fatal-warnings.patch" # bug 695446
 	"${FILESDIR}/${PN}-5.14.2-icu67.patch" # bug 720054
 	"${FILESDIR}/${P}-gcc-10.patch" # bug 721876
+	"${FILESDIR}/${P}-bison-3.7-build.patch" # bug 734356
 )
 
 src_prepare() {