misc/cgo/testsanitizer: don't run msan tests if msan doesn't work

Confirm that a trivial executable can build and execute using
-fsanitize=memory.

Fixes #18335 (by skipping the tests when they don't work).

Change-Id: Icb7a276ba7b57ea3ce31be36f74352cc68dc89d5
Reviewed-on: https://go-review.googlesource.com/34505
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

misc/cgo/testsanitizers/test.bash

@@ -24,8 +24,14 @@ msan=yes
 
 TMPDIR=${TMPDIR:-/tmp}
 echo 'int main() { return 0; }' > ${TMPDIR}/testsanitizers$$.c
-if $CC -fsanitize=memory -c ${TMPDIR}/testsanitizers$$.c -o ${TMPDIR}/testsanitizers$$.o 2>&1 | grep "unrecognized" >& /dev/null; then
-  echo "skipping msan tests: -fsanitize=memory not supported"
+if $CC -fsanitize=memory -o ${TMPDIR}/testsanitizers$$ ${TMPDIR}/testsanitizers$$.c 2>&1 | grep "unrecognized" >& /dev/null; then
+  echo "skipping msan tests: $CC -fsanitize=memory not supported"
+  msan=no
+elif ! test -x ${TMPDIR}/testsanitizers$$; then
+  echo "skipping msan tests: $CC -fsanitize-memory did not generate an executable"
+  msan=no
+elif ! ${TMPDIR}/testsanitizers$$ >/dev/null 2>&1; then
+  echo "skipping msan tests: $CC -fsanitize-memory generates broken executable"
   msan=no
 fi
 rm -f ${TMPDIR}/testsanitizers$$.*