python3-flit-core: bootstrap explicitly

Add a method to python_flit_core.bbclass that does a manual build with
flit explicitly, and use that to bootstrap python3-flit-core-native which
can build itself.

(From OE-Core rev: e902578c2c9aacdc83dcfa517bc1e57667fcc460)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/python_flit_core.bbclass

@@ -3,3 +3,8 @@ inherit python_pep517 python3native python3-dir setuptools3-base
 DEPENDS += "python3 python3-flit-core-native"
 
 PEP517_BUILD_API = "flit_core.buildapi"
+
+python_flit_core_do_manual_build () {
+    cd ${PEP517_SOURCE_PATH}
+    nativepython3 -m flit_core.wheel --outdir ${PEP517_WHEEL_PATH} .
+}

meta/recipes-devtools/python/python3-flit-core_3.7.1.bb

@@ -20,6 +20,10 @@ DEPENDS:append:class-native = " unzip-native"
 PYPI_PACKAGE = "flit"
 PEP517_SOURCE_PATH = "${S}/flit_core"
 
+do_compile:class-native () {
+    python_flit_core_do_manual_build
+}
+
 do_install:class-native () {
     python_pep517_do_bootstrap_install
 }