unity8: initial packaging (!27)

* Mir starts up and is able to display system settings
* x86_64 only for now, because at least ubuntu-app-test did not build
  on aarch64

Based on PureTryOut's work. Getting it to this stage was a huge effort
(as it shows in the package count: 111(!)). See the merge request for
details.

[skip ci]: this won't finish in CI; ollieparanoid made sure that
           everything builds for x86_64.

unity8/platform-api/0001-Use-proper-GTest.patch

@@ -0,0 +1,37 @@
+From 1289c8754848b1b95d89037aea6ddf3bde3534db Mon Sep 17 00:00:00 2001
+From: Luca Weiss <luca@z3ntu.xyz>
+Date: Sat, 12 Jan 2019 14:12:54 +0100
+Subject: [PATCH 1/3] Use proper GTest
+
+---
+ CMakeLists.txt       | 2 --
+ tests/CMakeLists.txt | 2 +-
+ 2 files changed, 1 insertion(+), 3 deletions(-)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index d5076b4..e6e5485 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -84,6 +84,4 @@ add_subdirectory(examples/)
+ 
+ #### Enable tests
+ include(CTest)
+-set(GTEST_ROOT /usr/src/gtest)
+ add_subdirectory(tests/)
+-add_subdirectory(${GTEST_ROOT} ${CMAKE_CURRENT_BINARY_DIR}/gtest)
+diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
+index 2b7204f..659510c 100644
+--- a/tests/CMakeLists.txt
++++ b/tests/CMakeLists.txt
+@@ -1,7 +1,7 @@
+ find_package(PkgConfig REQUIRED)
+ pkg_check_modules(PROCESS_CPP process-cpp REQUIRED)
+ 
+-include_directories(${GTEST_ROOT}/src)
++find_package(GTest)
+ include_directories(${PROCESS_CPP_INCLUDE_DIRS})
+ 
+ set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --std=c++11")
+-- 
+2.20.1
+