build: Introduce meson as the new build-system

Signed-off-by: Rahix <rahix@rahix.de>

meson.build

+project(
+  'card10-firmware',
+  'c',
+  default_options: [
+    'buildtype=minsize',
+    'c_lto=true',
+    'c_std=c99',
+    'b_staticpic=false',
+    'b_asneeded=false',
+  ],
+)
+
+assert(
+  meson.is_cross_build(),
+  'card10-firmware can only be cross-compiled for card10.\n' +
+  'Please use `--cross-file card10-cross.ini`.',
+)
+
+add_global_arguments(
+  meson.get_cross_property('target_defs'),
+  language: 'c',
+)
+
+add_global_link_arguments(
+  '-Wl,--gc-sections',
+  '-lm',
+  language: 'c',
+)
+
+subdir('lib/')
+subdir('hw-tests/')