Specify libtinfo5 legacy package for building on Ubuntu 20.04

Bug: None
Change-Id: I21c06e62379b241ef6e920037f595cb2646ea6ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2377186Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Kouhei Ueno <kouhei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801641}

build/install-build-deps.sh

@@ -473,6 +473,9 @@ elif package_exists libssl1.0.2; then
 else
   nacl_list="${nacl_list} libssl1.0.0:i386"
 fi
+if package_exists libtinfo5; then
+  nacl_list="${nacl_list} libtinfo5"
+fi
 if package_exists libpng16-16; then
   lib_list="${lib_list} libpng16-16"
 else