test: CC needs to be set to clang for fuzzing

Add a check if clang is used for fuzzing and error out if not.

Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>

diff --git a/configure.ac b/configure.ac
index e46605f..b93b51e 100644
--- a/configure.ac
+++ b/configure.ac

@@ -357,6 +357,8 @@
                        AC_MSG_ERROR("Fuzzing TCTI is meant to be built as the only TCTI"), [])
             AM_COND_IF([ENABLE_TCTI_MSSIM],
                        AC_MSG_ERROR("Fuzzing TCTI is meant to be built as the only TCTI"), [])
+            AS_IF([test "x$CC" != "xclang"],
+                       AC_MSG_ERROR("Fuzzing TCTI can only be used with clang"), [])
             ], [])
 
 AC_OUTPUT