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.

main/process-cpp/0001-Musl-libc-fixes.patch

@@ -0,0 +1,55 @@
+From 9e25c80e0e45c21dedc785019be95c0bbff4174d Mon Sep 17 00:00:00 2001
+From: Luca Weiss <luca@z3ntu.xyz>
+Date: Sun, 30 Dec 2018 18:01:32 +0100
+Subject: [PATCH] Musl libc fixes
+
+---
+ include/core/posix/standard_stream.h | 5 +++++
+ src/CMakeLists.txt                   | 1 +
+ src/core/posix/signal.cpp            | 2 +-
+ 3 files changed, 7 insertions(+), 1 deletion(-)
+
+diff --git a/include/core/posix/standard_stream.h b/include/core/posix/standard_stream.h
+index f50a9b7..1927fa8 100644
+--- a/include/core/posix/standard_stream.h
++++ b/include/core/posix/standard_stream.h
+@@ -23,6 +23,11 @@
+ 
+ #include <cstdint>
+ 
++// Musl uses "#define stdin (stdin)", so the enum declaration fails with a syntax error
++#undef stdin
++#undef stdout
++#undef stderr
++
+ namespace core
+ {
+ namespace posix
+diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
+index 063ece1..2a9dc15 100644
+--- a/src/CMakeLists.txt
++++ b/src/CMakeLists.txt
+@@ -45,6 +45,7 @@ target_link_libraries(
+ 
+   ${Boost_LIBRARIES}
+   ${CMAKE_THREAD_LIBS_INIT}
++  execinfo
+ )
+ 
+ # We compile with all symbols visible by default. For the shipping library, we strip
+diff --git a/src/core/posix/signal.cpp b/src/core/posix/signal.cpp
+index 9c80f21..ce8bbc1 100644
+--- a/src/core/posix/signal.cpp
++++ b/src/core/posix/signal.cpp
+@@ -151,7 +151,7 @@ public:
+             {
+                 auto result = ::read(scope.signal_fd, signal_info, sizeof(signal_info));
+ 
+-                for (uint i = 0; i < result / sizeof(signalfd_siginfo); i++)
++                for (unsigned int i = 0; i < result / sizeof(signalfd_siginfo); i++)
+                 {
+                     if (has(static_cast<core::posix::Signal>(signal_info[i].ssi_signo)))
+                     {
+-- 
+2.20.1
+