meta-phosphor: btrfs-tools: disable python PACKAGECONFIG

Some systems, like Bletchley, might be using btrfs file systems and
using the btrfs-tools to format them.  They probably don't need the
Python modules by default, so disable them in meta-phosphor.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I87316001f48432db4297656838b750e10651d043
diff --git a/meta-phosphor/conf/distro/include/phosphor-base.inc b/meta-phosphor/conf/distro/include/phosphor-base.inc
index 5eff315..b1f8d59 100644
--- a/meta-phosphor/conf/distro/include/phosphor-base.inc
+++ b/meta-phosphor/conf/distro/include/phosphor-base.inc
@@ -1,4 +1,5 @@
 require conf/distro/include/phosphor-defaults.inc
+require conf/distro/include/phosphor-pkg-tweaks.inc
 
 # Match the distro codename from upstream poky.
 DISTRO_CODENAME ?= "mickledore"
diff --git a/meta-phosphor/conf/distro/include/phosphor-pkg-tweaks.inc b/meta-phosphor/conf/distro/include/phosphor-pkg-tweaks.inc
new file mode 100644
index 0000000..a5c1df8
--- /dev/null
+++ b/meta-phosphor/conf/distro/include/phosphor-pkg-tweaks.inc
@@ -0,0 +1,7 @@
+## Some packages do not allow a simple bbappend to tweak the PACKAGECONFIG
+## because they can end up inheriting bbclasses, which cause other
+## side-effects before the bbappend is applied.  Place tweaks for those
+## packages in this file.
+
+# Disable python from btrfs-tools
+PACKAGECONFIG:remove:pn-btrfs-tools = "python"