added required deps to build qtwebengine

[boussaffawalid]

qt/5.x.x

Egl system library is needed when building qtwebengine on Linux, without it I got this warning

WARNING: Khronos development headers required to build QtWebEngine are missing (see mesa/libegl1-mesa-dev)
WARNING: QtWebEngine will not be built.

---

• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the conan-center hook activated.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

wboussafa seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[ghost]

I detected other pull requests that are modifying qt/5.x.x recipe:

• [qt5] dont require non needed deps when multiconfiguration is set to True #11566
• del qtmacextras option for non Macos and delete qtwinextras for non … #11449

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[conan-center-bot]

Failure in build 1 (b9ef48c3fb98fa501c570b93199cb8014aa9ec02):

• qt/5.15.2@:
  Didn't run or was cancelled before finishing

• qt/5.15.3@:
  Didn't run or was cancelled before finishing

• qt/5.15.5@:
  Didn't run or was cancelled before finishing

• qt/5.15.4@:
  An unexpected error happened and has been reported

---

^{Note: To save resources, CI tries to finish as soon as an error is found. For this reason you might find that not all the references have been launched or not all the configurations for a given reference. Also, take into account that we cannot guarantee the order of execution as it depends on CI workload and workers availability.}

[ericLemanissier]

@boussaffawalid thanks for the pull requests. Can you gather all the changes on qt5 recipe in a single pull recipe, to reduce the impact on CI server? Because qt is really long to compile. Thanks again!

[boussaffawalid]

replaced with #11619

[boussaffawalid]

@ericLemanissier here is the new PR #11619