wmxml2: don't do out-of-tree builds manually

cmake.bbclass as of oe-core 783fb88 defaults to out-of-tree builds.  Use that
functionality instead of passing arguments to EXTRA_OECMAKE and _prepends.

Signed-off-by: Ross Burton <ross.burton@intel.com>
Reviewed-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

meta-oe/recipes-support/opensync/wbxml2_0.10.8.bb

@@ -15,17 +15,7 @@ S = "${WORKDIR}/libwbxml-${PV}"
 
 inherit cmake pkgconfig
 
-EXTRA_OECMAKE += " . -B${WORKDIR}/build "
-
 PACKAGES += "${PN}-tools"
 
 FILES_${PN}-tools = "${bindir}"
 FILES_${PN} = "${libdir}/*.so.*"
-
-do_build_prepend() {
-    cd ${WORKDIR}/build
-}
-
-do_install_prepend() {
-    cd ${WORKDIR}/build
-}