unit-test: meson: update flags for phosphor-logging

Prep build scripts for phosphor-logging migration to meson
by adding openpower phosphor-logging build options.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I9252e465e7a171455ed95c3723d1ca13b561a5ae
diff --git a/scripts/unit-test.py b/scripts/unit-test.py
index 29545dc..b8f9bcb 100755
--- a/scripts/unit-test.py
+++ b/scripts/unit-test.py
@@ -1109,7 +1109,9 @@
     # MESON_FLAGS = [GIT REPO]:[MESON FLAGS]
     MESON_FLAGS = {
         'phosphor-dbus-interfaces':
-        ['-Ddata_com_ibm=true', '-Ddata_org_open_power=true']
+        ['-Ddata_com_ibm=true', '-Ddata_org_open_power=true'],
+        'phosphor-logging':
+        ['-Dopenpower-pel-extension=enabled']
     }
 
     # DEPENDENCIES = [MACRO]:[library/header]:[GIT REPO]