community/filezilla: include assert.h

Files in engine/ refer to assert, but `assert.h` is not included for
some reason. Passing `-include assert.h` via `CXXFLAGS` fixes this.

community/filezilla/APKBUILD

@@ -12,6 +12,7 @@ subpackages="$pkgname-doc $pkgname-lang"
 source="https://download.filezilla-project.org/client/FileZilla_${pkgver}_src.tar.bz2"
 
 build() {
+	export CXXFLAGS="$CXXFLAGS -include assert.h"
 	./configure \
 		 --prefix=/usr \
 		--sysconfdir=/etc \