libgpiod: Enable CXX Headers

Add CXX to packageconfig and change the devtools to
RDEPEND on libgpiod-tools instead as they are the actual
tools. Without changing it to the tools when we enable
cxx the tools do not by default get installed by Yocto.

Tested: gpioinfo still functioned properly on BMC, and was
able to bitbake package using CXX headers for dbus-sensors.

(From meta-phosphor rev: 76d4c46294c83ea0240a319b4e74c06b57dc51c1)

Change-Id: I5143130bbfbe97f8af4818231d502f36f88fe4ae
Signed-off-by: James Feist <james.feist@linux.intel.com>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-phosphor/recipes-support/libgpiod/libgpiod_%.bbappend b/meta-phosphor/recipes-support/libgpiod/libgpiod_%.bbappend
new file mode 100644
index 0000000..0ee1845
--- /dev/null
+++ b/meta-phosphor/recipes-support/libgpiod/libgpiod_%.bbappend
@@ -0,0 +1 @@
+PACKAGECONFIG += " cxx"