package/qt5/qt5webengine: fix build with Bison 3.7

package/qt5/qt5webengine: fix build with Bison 3.7

Add patch from upstream that fixes build with Bison 3.7.

There are no autobuilder failures for this issue, but the following
defconfig:

BR2_arm=y
BR2_cortex_a8=y
BR2_TOOLCHAIN_EXTERNAL=y
BR2_INIT_NONE=y
BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV=y
BR2_SYSTEM_BIN_SH_NONE=y
BR2_PACKAGE_QT5=y
BR2_PACKAGE_QT5WEBENGINE=y
BR2_PACKAGE_RPI_USERLAND=y

Failed with:

/home/thomas/buildroot/buildroot/output/build/qt5webengine-5.15.0/src/core/release/gen/third_party/blink/renderer/core/xpath_grammar.cc:124:10: fatal error: xpath_grammar.hh: No such file or directory
  124 | #include "xpath_grammar.hh"
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.

With this patch applied, it builds fine.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
[yann.morin.1998@free.fr: add url to upstream commit, provided by Peter]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>