meson: add subprojects to build

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ia7a24e92715cca5ee890d67d7b645feada4ec68b
diff --git a/subprojects/phosphor-logging.wrap b/subprojects/phosphor-logging.wrap
new file mode 100644
index 0000000..a039fcf
--- /dev/null
+++ b/subprojects/phosphor-logging.wrap
@@ -0,0 +1,3 @@
+[wrap-git]
+url = https://github.com/openbmc/phosphor-logging.git
+revision = HEAD