oe-selftest: add a cpp-example recipe

This simple C++ project supports compilation with CMake and Meson.
(Autotool support could be added later on.)
It's supposed to be used with oe-selftest.

An artificial project has several advantages over compiling a normal
CMake or Meson based project for testing purposes:
- It is much faster because it can be kept minimalistic
- It can cover multiple odd corner cases
- No one will change it in an unpredictable way
- It can support multiple build tools with only one C++ codebase

(From OE-Core rev: 4904e772470b0d6e5d98ef0344b3f2bf54214661)

Signed-off-by: Adrian Freihofer <adrian.freihofer@siemens.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-selftest/recipes-test/cpp/cmake-example.bb

@@ -0,0 +1,25 @@
+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: MIT
+#
+
+SUMMARY = "A C++ example compiled with cmake."
+
+require cpp-example.inc
+
+SRC_URI += "file://CMakeLists.txt"
+
+inherit cmake-qemu
+
+PACKAGECONFIG[failing_test] = "-DFAILING_TEST=ON"
+
+FILES:${PN}-ptest += "${bindir}/test-cmake-example"
+
+do_run_tests () {
+    bbnote ${DESTDIR:+DESTDIR=${DESTDIR} }${CMAKE_VERBOSE} cmake --build '${B}' --target test -- ${EXTRA_OECMAKE_BUILD}
+    eval ${DESTDIR:+DESTDIR=${DESTDIR} }${CMAKE_VERBOSE} cmake --build '${B}' --target test -- ${EXTRA_OECMAKE_BUILD}
+}
+do_run_tests[doc] = "Run cmake --target=test using qemu-user"
+
+addtask do_run_tests after do_compile