fix(aur): Use newest xpp commit to build with xcb-proto

xcb-proto 1.13 finally introduces the eventstruct key that made polybar
not compile. The fix isn't in any release yet, this checks out the
newest xpp commit with the fix during compilation until we release 3.2.0

Fixes #1090

contrib/polybar.aur/PKGBUILD

@@ -2,7 +2,7 @@
 # Contributor: Michael Carlberg <c@rlberg.se>
 pkgname=polybar
 pkgver=3.1.0
-pkgrel=2
+pkgrel=3
 pkgdesc="A fast and easy-to-use status bar"
 arch=("i686" "x86_64")
 url="https://github.com/jaagr/polybar"
@@ -23,6 +23,7 @@ md5sums=("SKIP")
 
 prepare() {
   git -C "${pkgname}" submodule update --init --recursive
+  git -C "${pkgname}/lib/xpp" checkout 00165e1a6d5dd61bc153e1352b21ec07fc81245d
   mkdir -p "${pkgname}/build"
 }