build: meson support for phosphor-log-manager

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I5400d21d59b3c1ff8bde61d80eaec1cb6701a8cb
diff --git a/gen/README b/gen/README
new file mode 100644
index 0000000..71182b5
--- /dev/null
+++ b/gen/README
@@ -0,0 +1,2 @@
+This directory contains generated meson.build files from sdbus++-gen-meson.
+Do not edit them by hand.