meson: Define our own clang-tidy target

meson's target has a few issues:
- Runs on all source files regardless if they're included in the
  build or not
- Doesn't have any dependencies on generated sources which means we
  have to do a full build first before we can run clang-tidy
- Doesn't allow us to pass any extra arguments

To work around these, let's define our own clang-tidy target instead
using llvm's run-clang-tidy script. Alongside the clang-tidy target,
let's start keeping track of all generated sources which we make the
clang-tidy target depend on. We also add a new target which will only
generate source files which is useful for setting up the source tree
for running code analysis against it.

Author: DaanDeMeyer

meson.build

@@ -37,9 +37,11 @@ if conf.get('ENABLE_UKIFY') == 1
                 capture : true,
                 build_by_default : want_tests != 'false')
 else
-        test_hwids_section_c = ''
+        test_hwids_section_c = []
 endif
 
+generated_sources += test_hwids_section_c
+
 executables += [
         efi_test_template + {
                 'sources' : files('test-bcd.c'),