[PATCH 1/3] meta-selftest/poison: improve sysroot poisoning test case

[Ross Burton <ross.burton@arm.com>]

It was discovered by Martin Jansa that the sysroot poisoning errors are
not functioning as they should. Due to either a bug from day 1 or a
bad rebase, -Werror=poison-system-directories is only passed when GCC
is invoking _just_ the preprocessor, not the compiler.

Demonstrate this by expanding the test case to exercise not just $CPP,
but also $CC for both C and C++ languages. This improved test case now
fails.

Signed-off-by: Ross Burton <ross.burton@arm.com>
---
 meta-selftest/recipes-test/poison/poison.bb | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/meta-selftest/recipes-test/poison/poison.bb b/meta-selftest/recipes-test/poison/poison.bb
index 7ace901cc3a..e9eee0cdbab 100644
--- a/meta-selftest/recipes-test/poison/poison.bb
+++ b/meta-selftest/recipes-test/poison/poison.bb
@@ -9,8 +9,12 @@ inherit nopackages
 # will result in compiler errors.  This recipe should will fail to build and
 # oe-selftest has a test that verifies that.
 do_compile() {
-    touch empty.c
-    ${CPP} ${CFLAGS} -I/usr/include empty.c
+    bbnote Testing preprocessor
+    echo "int main(int argc, char** argv) {}" | ${CPP} -I/usr/include -
+    bbnote Testing C compiler
+    echo "int main(int argc, char** argv) {}" | ${CC} -x c -I/usr/include -
+    bbnote Testing C++ compiler
+    echo "int main(int argc, char** argv) {}" | ${CC} -x c++ -I/usr/include -
 }
 
 EXCLUDE_FROM_WORLD = "1"
-- 
2.34.1